Subject: Linux Ethernet HOWTO (Part 1/2)
From: Paul Gortmaker <[email-masked]>
Newsgroups: comp.os.linux.announce,comp.os.linux.admin,comp.answers,news.answers

Archive-Name: linux/howto/ethernet/part1
Last-Modified: 16 Mar 1994

Linux Ethernet HOWTO v1.0 -- Last updated Mar 16, 1994
=================================================================

-- covers changes up to and including Linux kernel v1.0

INDEX:

0	Introduction.
0.01		How do I use this Guide?
0.01		Disclaimer and Copyright
0.02		Questions already?
0.03		Related Documentation
0.04		New Versions of this Document
0.05		Feedback

1	What card should I buy for Linux?
1.01		Eight bit vs 16 bit
1.02		Low price Ethernet cards
1.03		Vendors and brands to avoid.
1.04		Type of cable that your card should support

2	Status of various Ethernet cards under Linux.
2.01		3Com
2.02		Western Digital / SMC
2.03		NExxxx
2.04		Hewlett Packard Cards
2.05		D-Link
2.06		Cabletron
2.07		Allied Telesis
2.08		Arcnet
2.09		Digital / DEC
2.10		Intel
2.11		PureData
2.12		Xircom
2.13		Zenith
2.14		Racal-Interlan
2.15		AMD LANCE (79C960)
2.16		AT-Lan-Tec / RealTek Pocket adaptor
2.17		Ansel
2.18		DFI

3	Clones of popular Ethernet cards.
3.01		WD80x3 Clones
3.02		NE2000 Clones

4	Cables, coax, twisted pairs etc.
4.01		Thin Ethernet (thinnet)
4.02		Twisted Pair
4.03		Thick Ethernet

5	Technical information.
5.01		Probed addresses
5.02		Skeleton / prototype driver
5.03		Driver interface to the kernel
5.04		Interrupts and linux
5.05		Programmed I/O vs. shared mem. vs slave/master DMA
5.06		Programming the Intel chips (i82586 and i82593)
5.07		Programming information from 3Com
5.08		Notes on AMD PCnet-ISA / LANCE Based cards (79C960)
5.09		Multicast and Promiscuous mode
5.10		The Berkeley Packet Filter (BPF)
5.11		Unresolved questions / concerns

6	Possible problems, questions and troubleshooting.
6.01		Problems with NE2000 (and clones)
6.02		Problems with WD80*3 cards
6.03		Problems with 3Com cards

7	Networking with a laptop computer.
7.01		Option 1 -- using SLIP
7.02		Option 2 -- Built in NE2000 compatible or PCMCIA Ethercard.
7.03		Option 3 -- ISA Ethercard in the docking station.
7.04		Option 4 -- Pocket / parallel port adaptors.

8	Frequently asked questions.
8.01		Just the FAQ's ma'am -- just the FAQ's.

9	Miscellaneous.
9.01		Bad Vendors
9.02		Closing

======================================================================

0. Introduction.

	This is the Ethernet-HOWTO, which is a compilation of information
	about which ethernet devices can be used for Linux, and how to
	set them up.

	This Ethernet-HOWTO is by:
		Donald J. Becker	<[email-masked]>
		Paul Gortmaker		<[email-masked]>

	It covers what cards you should and shouldn't buy; how to set
	them up, how to run more than one, and other common problems and
	questions. It does *not* cover the software end of things, as that
	is covered in the NET-2 HOWTO.

	Other people who have contributed (directly or indirectly) are,
	in alphabetical order:

	Peter Bauer		<[email-masked]>
	Ross Biro		<[email-masked]>
	Alan Cox		<[email-masked]>
	David C. Davies		<[email-masked]>
	Bjorn Ekwall		<[email-masked]>
	Charles Hedrick		<[email-masked]>
	Mike Jagdis		<[email-masked]>
	Duke Kamstra		<[email-masked]>
	Russell Nelson		<[email-masked]>
	Cameron Spitzer		<[email-masked]>
	Dave Roberts		<[email-masked]>
	Glenn Talbott		<[email-masked]>
	Miquel van Smoorenburg	<[email-masked]>

	Many thanks to the above people, and all the other unmentioned
	testers out there.

0.01 How Do I Use This Guide?

	As this guide is getting bigger and bigger, you probably don't want
	to spend the rest of your afternoon reading the whole thing. And you
	don't *have* to read it all. If you haven't got an ethernet card, then
	you will want to start with section one to see what you should buy,
	and what you should avoid. If you have already got an ethernet card,
	but are not sure if you can use it with Linux, then you will want to
	read section two, which contains specific information on each
	manufacturer, and their cards. If you are having trouble with your
	card, then you will want to read the specific information about
	your card in section two and the troubleshooting information in
	section six. If you are interested in some of the technical aspects
	of the device drivers, then you can find that information in
	section 5.

0.01 Disclaimer and Copyright

	This document is *not* gospel. However, it is probably the most
	up to date info that you will be able to find. Nobody is responsible
	for what happens to your hardware but yourself. If your ethercard
	or any other hardware goes up in smoke (...nearly impossible!)
	we take no responsibility. ie. THE AUTHORS ARE NOT RESPONSIBLE
	FOR ANY DAMAGES INCURRED DUE TO ACTIONS TAKEN BASED ON THE
	INFORMATION INCLUDED IN THIS DOCUMENT.

	This document is Copyright (c) 1994 by Donald Becker and
	Paul Gortmaker. Permission is granted to make and distribute
	verbatim copies of this manual provided the copyright notice
	and this permission notice are preserved on all copies.

	Permission is granted to copy and distribute modified versions
	of this document under the conditions for verbatim copying,
	provided that this copyright notice is included exactly as in
	the original, and that the entire resulting derived work is
	distributed under the terms of a permission notice identical
	to this one.

	Permission is granted to copy and distribute translations
	of this document into another language, under the above
	conditions for modified versions.

0.02 Questions already?

	If you have questions about your ethernet card, please READ this
	document first. You may also want to join the NET channel of the
	Linux-activists mailing list by sending mail to
		[email-masked]
	with the line
		X-Mn-Admin: join NET
	at the top of the message body (not the subject). If you want to
	learn how to use the mailing channels, then send an empty message
	to the above address, and you will get an instruction manual sent
	back to you in a few hours. However, it is worth noting that the NET
	channel is primarily used for discussion of the networking code, and
	you may not see much discussion about a particular driver.
	Furthermore keep in mind that the NET channel is for development
	discussions only. General questions on how to configure your system
	should be directed to comp.os.linux.help unless you are actively
	involved in the development of part of the networking for Linux.
	We ask that you *please* respect this general guideline for content.
	You can safely bet that neither of the authors will respond to
	any plea for help that *should* be posted to c.o.l.help, but is
	inappropriately placed elsewhere.

0.03 Related Documentation

	Much of this info came from saved postings from the comp.os.linux
	groups, which shows that it is a valuable resource of information.
	Other useful information came from a bunch of small files by Donald
	himself. Some of these are found at /pub/linux/info on ftp.super.org
	[192.31.192.1] Of course, if you are setting up an Ethernet card,
	then you will want to read the NET-2 HOWTO so that you can actually
	do something with it. ftp.super.org is the home of most alpha drivers
	that are not presently in the kernel. And last but not least, the
	contributions from the individuals and companies listed above are
	greatly appreciated as well. Oh yeah, if you fancy yourself as
	a bit of a hacker, you can always scrounge some additional info
	from the driver source files as well. There is usually a paragraph
	in there describing any important points.

0.04 New versions of this document

	New versions of this document can be retrieved via anonymous
	FTP from sunsite.unc.edu:/pub/Linux/docs/HOWTO/* and various
	Linux ftp mirror sites. It will also be posted to the newsgroup
	comp.os.linux.announce at a regular interval. Updates will be made
	as new information / drivers becomes available. If this copy
	that you are reading is more than 2 months old, it is either out of
	date, or it means that I have been lazy and haven't updated it.

0.05 Feedback

	Any corrections can be sent to one of us ([email-masked]
	or [email-masked]) We will *attempt* to keep this up to date as
	more drivers become available, and as the networking code matures.

1 What card should I buy for Linux?

	For impatient users that just want a quick, cheap answer the
	summary is: get 16 bit thinnet 8013 cards. For more detail as
	to the who what where and why, read on.

1.01 Eight bit vs 16 bit

	Unless you are a light user, or are confined to using the smaller
	ISA slot, the use of the 8 bit cards like the wd8003 and the 3c503
	is really not worth the cost savings. Get the 8013 or the 3c503/16
	instead.

1.02 Low price Ethernet cards

	I keep track of the current low-price vendors, just because it's
	asked so often. Call AT-LAN-TEC at 301-948-7070. Ask for their
	technical support person, "Vincent Bono". As with all purchases,
	you should indicate you are buying this for a Linux system.
	The last I checked the price for 10 NE2000s was $480, or $48 ea.!
	NB: Their current NE2000 clone is a model that "traps" other
	drivers that probe into their address space. AT-LAN-TEC also carries
	a clone, non-EEPROM 8013 board for somewhat more, and a NE2100 clone.
	Either is a better choice if the very lowest price isn't essential.
	Also, SMC is offering an evaluation deal on their new Ultra cards,
	and the word is that you can get one for $50. You can ask them
	yourself by calling 1-800-SMC-4YOU in Canada and the USA.

	The Allied Telesis AT1500 is offered at a good price by many vendors.
	Even Inmac, known for their premium markup, has this card for under
	$100.

1.03 Vendors and Brands to Avoid

	These vendors have decided *not* to release programming information
	about their products, without signing a non-disclosure agreement.
	More information can be found in section two and 9.01. Hence it is
	strongly advised that you avoid buying products offered from
	these companies.

		(1) Cabletron
		(2) Xircom

	These particular cards should be avoided, as they are obsolete.
	The reasons as to why they have been classified as such can be
	found in section 2 of this document.

		(1) 3c501
		(2) Arcnet

1.04 Type of cable that your card should support

	Unless you have to conform to an existing network, you will want
	to use thinnet or thin ethernet cable. This is the style with the
	standard BNC connectors. See section 4 for other concerns with
	different types of ethernet cable.

	Most ethercards also come in a "Combo" version for only $10-$20 more.
	These have both twisted pair and thinnet transceiver built-in,
	allowing you to change your mind later.

2 Status of Various Ethernet Cards under Linux

	The only thing that one needs to use an ethernet card with Linux
	is the appropriate driver. For this, it is essential that the
	manufacturer will release the technical programming information to
	the general public without you (or anyone) having to sign your life
	away. A good guide for the likelihood of getting documentation
	(or, if you aren't writing code, the likelihood that someone
	else will write that driver you really, really need) is the
	availability of the Crynwr (nee Clarkson) packet driver. Russ
	Nelson (see the acknowledgements in the intro.) runs this
	operation, and has been very helpful in supporting the development
	of drivers for Linux.

	Given the documentation, you can write a driver for
	your card and use it for Linux, at least in theory. Keep in
	mind that some old hardware that was designed for XT type
	machines will not function very well in a multitasking
	environment such as Linux. Use of these will lead to major
	problems if your network sees a reasonable amount of traffic.

	Most cards come with drivers for MS-DOS interfaces such as
	NDIS and ODI, but these are useless for Linux. Many people
	have suggested directly linking them in or automatic
	translation, but this is nearly impossible. The MS-DOS
	drivers expect to be in 16 bit mode and hook into "software
	interrupts", both incompatible with the Linux kernel. This
	incompatibility is actually a feature, as some Linux drivers
	are considerably better than their MS-DOS counterparts. The
	"8390" series drivers, for instance, use ping-pong transmit
	buffers, which are only now being introduced in the MS-DOS world.

	Keep in mind that PC ethercards have the widest variety of
	interfaces (shared memory, programmed I/O, bus-master, or slave
	DMA) of any computer hardware for anything, and supporting a
	new ethercard sometimes requires re-thinking most of the lower-level
	networking code. (If you are interested in learning more about
	these different forms of interfaces, see section 5)

	Also, similar product numbers don't always indicate similar products.
	For instance, the 3c50* product line from 3Com varies wildly
	between different members.

	Enough talk. Let's get down to the information you want.

2.01 3Com

	Supported:

		3c503, 3c503/16
			3Com shared-memory ethercards. They also have a
			programmed I/O mode that doesn't use the 8390
			facilities (their engineers found too many bugs!)
			It should be about the same speed as the same bus
			width WD80x3, but I don't have a 16 bit version
			to benchmark. Unless you are a light user, spend
			the extra money and get the 16 bit model, as the
			price difference isn't significant. The 3c503 does not
			have "EEPROM setup", so the diagnostic/setup program
			isn't needed before running the card with Linux. The
			shared memory address of the 3c503 is set using jumpers
			that are shared with the boot PROM address. This is
			confusing to people familiar with other ISA cards,
			where you always leave the jumper set to "disable"
			unless you have a boot PROM.

			The Linux 3c503 driver can also work with the 3c503
			programmed-I/O mode, but this is slower and less
			reliable than shared memory mode. Also, programmed-I/O
			mode is not tested when updating the drivers, the
			deadman (deadcard?) check code may falsely timeout on
			some machines, and the probe for a 3c503 in
			programmed-I/O mode is turned off by default in some
			versions of the kernel. This was a panic reaction to
			the general device driver probe explosion; the 3c503
			shared memory probe is a safe read from memory, rather
			than an extensive scan through I/O space. As of pl13,
			the kernel has an I/O port registrar that makes I/O
			space probes safer, (see section 5.1 for more info.)
			and the programmed-I/O 3c503 probe has been re-enabled.
			You still shouldn't use the programmed-I/O mode though,
			unless you need it for MS-DOS compatibility.

			The 3c503's IRQ line is set in software, with no hints
			from an EEPROM. Unlike the MS-DOS drivers, the
			Linux driver has capability to autoIRQ: it uses the
			first available IRQ line in {5,2/9,3,4}, selected each
			time the card is 'ifconfig'ed. (Older driver versions
			selected the IRQ at boot time.) The ioctl() call
			in 'ifconfig' will return EAGAIN if no IRQ line is
			available at that time.

		3c509
			A fairly new card from 3Com. It's inexpensive and has
			excellent performance for a non-bus-master design. The
			drawbacks are that it _requires_ very low interrupt
			latency, and it isn't rated for bus speeds greater than
			8Mhz.

			A working 3c509 driver was first included as an
			alpha-test version in the 0.99pl13 kernel sources.
			It is now in the standard kernel.

			The 3c509 has a tiny Rx buffer, causing the driver to
			occasionally drop a packet if interrupts are masked for
			too long. To minimize this problem, the driver should
			be completely rewritten to use predictive interrupts.
			(Note: performance re-writes of working drivers are low
			priority unless there is some particular incentive or
			need.)

			There is also an alpha version of a Linux 3c509
			diagnostic and EEPROM setup program, but for now
			users that don't like the defaults should use the
			MS-DOS EEPROM setup program.

		3c579
			The EISA version of the 509. The current EISA version
			uses the same 16 bit wide chip rather than a 32 bit
			interface, so the performance increase isn't stunning.
			The EISA probe code was added to 3c509.c for pl14.
			We would be interested in hearing progress reports
			from any 3c579 users. (Read the above 3c509
			section for info on the driver.)

			Cameron Spitzer writes:
			"The 3C579 (Etherlink III EISA) should be configured
			as an EISA card. The IO Base Address (window 0
			register 6 bits 4:0) should be 1f, which selects EISA
			addressing mode. Logic outside the ASIC decodes the
			IO address s000, where s is the slot number. I don't
			think it was documented real well. Except for its IO
			Base Address, the '579 should behave EXACTLY like the
			'509 (EL3 ISA), and if it doesn't, I want to hear
			about it (at my work address).

			I will leave it to the Real Programmers to suggest
			the right hack to /usr/src/linux/net/inet/3c509.c to
			take care of the EISA case.

			(Note that the drivers now reside in ./drivers/net/
			 and *not* ./inet/net/ --- pg.)

			Beware that if you put a '509 in EISA addressing mode
			by mistake and save that in the EEPROM, you'll have
			to use an EISA machine or the infamous Test Via to
			get it back to normal, and it will conflict at IO
			location 0 which may hang your ISA machine. It's not
			my job to say whether this is a bug or feature, but I
			have heard loud and clear that customers don't like
			it and I don't think we'll do it that way again."

	Unsupported:

		3c501
			Too brain-damaged to use. Available surplus from many
			places. Avoid it like the plague. Again, do not
			purchase this card, even as a joke. It's performance
			is horrible, and it breaks in many ways.

			(I have a standing offer: I'll pay $2 for each 3c501
			shipped to me postpaid, but only if you include the
			BNC 'T' connector and the jumpers. $2.50 if you just
			send the 'T', jumpers, and address PROM and promise to
			destroy the board. -djb)

			Cameron L. Spitzer of 3Com said:
			"I'm speaking only for myself here, of course, but I
			believe 3Com advises against installing a 3C501 in a
			new system, mostly for the same reasons Donald has
			discussed. You probably won't be happy with the
			3C501 in your Linux box. The data sheet is marked
			"(obsolete)" on 3Com's Developers' Order Form, and
			the board is not part of 3Com's program for sending
			free Technical Reference Manuals to people who need
			them. The decade-old things are nearly
			indestructible, but that's about all they've got
			going for them any more."

			For those not yet convinced, the 3c501 can only do one
			thing at a time -- while you are removing one packet
			from the single-packet buffer it cannot receive
			another packet, nor can it receive a packet while are
			loading a transmit packet. This was fine for a
			network between two 8088-based computers where
			processing each packet and replying took 10's of
			msecs, but modern networks send back-to-back
			packets for almost every transaction.

			Having read this far, you must be persistent, so you
			get let in on a secret. As of pl13, some more of
			the hardware problems were "compensated for".

			Ie. in a fit of madness I wasted a whole day updating
			my 3c501 driver and then trying to track down a few
			more of the 3c501 glitches. It now works well enough
			to NFS mount filesystems, but the receiver still
			occasionally hangs. I'm mostly certain that this is
			a hardware bug. When it hangs, the next set of
			outgoing packets will reset the board, but that's
			only useful if you have something occasionally
			generating outgoing packets.

			The driver is now in the std. kernel, but under the
			following conditions: This is unsupported code. I
			know my usual copyright says all the code is
			unsupported, but this is _really_ unsupported. I
			DON'T want to see bug reports, and I'll accept bug
			fixes only if I'm in a good mood that day.

			I don't want to see a fest of "Linux ethercards for
			sale" postings. A bunch of people have bought dozens
			of "dumpster special" 3c501s, and they hope to sell
			them at rip-off prices. A 3c501 is barely worth the
			shipping cost, and if I see people trying to sell
			them here by claiming "supported by Linux" I _will_
			flame them. They are _not_ supported by Linux.

			I don't want to be flamed later for putting out bad
			software. I don't know all all of the 3c501 bugs,
			and I know this driver only handles a few that I've
			been able to figure out. It has taken a long
			intense effort just to get the driver working this
			well.

			That said, you will find it included in "config.in"
			No special mods are needed to use it with pl15
			or greater kernels. Jumper your card to 0x280.

			AutoIRQ works, DMA isn't used, the autoprobe only
			looks at 0x280, the debug level is set with the third
			boot-time argument. You'll probably want to change
			the default EL_DEBUG to '2'.

			Once again, THE USE OF A 3c501 IS STRONGLY DISCOURAGED
			and it is NOT SUPPORTED BY LINUX.

		3c505
			An Intel-based ethercard with no driver available
			at present. (Not a very common card.)

		3c507
			This card uses one of the Intel chips, and the
			development of the driver is closely related to
			the development of the Intel Ether Express driver.
			The driver has been included in the standard
			release of pl15. You will have to un-comment
			the 3c507 line in "config.in" -- in case you
			didn't figure it out already, it is commented
			out because it is still being tested.

			Technical information is available in section 5.06,
			and if you have experience in writing drivers, see
			section 5.07 as well.

2.02 Western Digital / SMC

	The ethernet part of Western Digital has been bought by SMC. The
	SMC Elite and SMC Elite Plus are the same as late-model WD8003
	and WD8013 cards. Note that the SMC Elite Ultra is *not* the
	same as the plain SMC Elite / WD8013 card. (see below)

	Supported:

		WD8003, WD8013, SMC Elite, SMC Elite Plus
			A shared memory design by Western Digital. The
			8 bit 8003 is slightly less expensive, but only
			worth the savings for light use. Over the
			years the design has added more registers and an
			EEPROM. Clones usually go by the '8013' name, and
			usually use a non-EEPROM (jumpered) design. This part
			of WD has been sold to SMC, so you'll usually see
			something like SMC/WD8013 or SMC Elite Plus (WD8013).
			The shared memory makes the cards 10-20% faster,
			especially with larger packets. More importantly
			(to me at least) it avoids a few bugs in the
			programmed-I/O mode of the 8390, allows safe
			multi-threaded access to the packet buffer, and
			doesn't have a programmed-I/O data register that
			hangs your machine during warm-boot probes.

		SMC Elite 16 ULTRA
			This ethercard is based on a new chip from SMC, with
			a few new features. While it has a mode that is
			similar to the older SMC ethercards, it's not
			compatible with the old WD80*3 drivers. However, in
			this mode it shares most of its code with the other
			8390 drivers, while operating somewhat faster than a
			WD8013 clone.

			Some of the device probe checks in pl14 were too
			too strict, causing some cards to not be detected
			every time. This was fixed for pl14a, and hence is
			fine for pl15. Since part of the Ultra "looks" like
			an 8013, the Ultra probe is supposed to find an
			Ultra before the wd8013 probe has a chance to
			mistakenly identify it.

			Std. as of pl14, and made possible by documentation
			and ethercard loan from [email-masked],
			Duke Kamstra. If you plan on using an Ultra with Linux
			send him a note of thanks to let him know that there
			are Linux users out there!

			I'm considering writing a separate driver for the
			Ultra's "Altego" mode which allows chaining transmits
			at the cost of inefficient use of receive buffers,
			but that will probably not happen right away.
			Performance re-writes of working drivers are low
			priority unless there is some particular incentive
			or need.

2.03 NExxxx

	The prefix "NE" came from Novell Ethernet. Novell followed the
	cheapest NatSemi databook design and sold the manufacturing rights
	(spun off?) Eagle, just to get reasonably-priced ethercards into
	the market.

	Supported:

		NE1000, NE2000
			The now-generic name for a bare-bones design around
			the NatSemi 8390. They use programmed I/O rather than
			shared memory, leading to easier installation but
			slightly lower performance and a few problems. Again,
			the savings of using an 8 bit NE1000 over the NE2000
			are only warranted if you expect light use. Some
			recently introduced NE2000 clones use the National
			Semiconductor "AT/LANTic" 83905 chip, which offers
			a shared memory mode similar to the 8013 and EEPROM
			or software configuration. Some problems can arise
			with poor clones. See the question and answer section
			later in this document, and the section on clones.
			I have written a NE2000 diagnostic program, but it
			is still presently in alpha test. (ne2k)

		NE1500, NE2100
			The AT1500 driver, recently added to the list of
			supported cards, also supports the NE1500, NE2100 and
			clones. The driver shipped with pl12 kernel doesn't
			detect non-AT1500 cards with autoprobe, but will work
			fine if you specify the base address explicitly and
			jumper for DMA channel 5. Read the Allied Telesis
			section for more information on LANCE based cards.

2.04 Hewlett Packard

	The 272** cards use programmed I/O, similar to the NE*000 boards,
	but the data transfer port can be "turned off" when you aren't
	accessing it, avoiding problems with autoprobing drivers.

	Thanks to Glenn Talbott for cleaning up the confusion in this
	section regarding the version numbers of the HP hardware, and
	adding lots of new info.

	Supported:

		27245A
			8 Bit 8390 based 10BaseT, not recommended for all the
			8 bit reasons. It was re-designed a couple years
			ago to be highly integrated which caused some
			changes in initialization timing which only
			affected testing programs, not LAN drivers. (The
			new card is not 'ready' as soon after switching
			into and out of loopback mode.)

		27247B, 27252A
			The 47B is a 16 Bit 8390 based 10BaseT w/AUI, and
			the 52A is a 16 Bit 8390 based ThinLAN w/AUI.
			These cards are high performers (3c509 speed) without
			the interrupt latency problems (32K onboard RAM for TX
			or RX packet buffering). They both offer LAN
			connector autosense, data I/O in I/O space (simpler) or
			memory mapped (faster), and soft configuration. 27247B
			was rated Best for ISA Servers by PC Mag this year.

		27247A
			This is the older model that existed before the "B".
			Two versions 27247-60001 or 27247-60002 have part
			numbers marked on the card. Functionally the same to
			the LAN driver, except bits in ROM to identify
			boards differ. -60002 has a jumper to allow
			operation in non-standard ISA busses (chipsets
			that expect IOCHRDY early.)

		HP J2405A
			These are lower priced, and slightly faster than the
			27247B/27252A, but are missing some features, such
			as AUI, ThinLAN connectivity, and boot PROM socket.
			This is a fairly generic LANCE design, but a minor
			design decision makes it incompatible with a generic
			"NE2100" driver. Special support for it (including
			reading the DMA channel from the board) is in pl14
			and up, thanks to information provided by HP's Glenn
			Talbott, [email-masked]. Note that the pre pl14
			driver should not be used with this card.

			More information on LANCE based cards can be found in
			section 5.08.

2.05 D-Link

	Supported:

		DE-600
			Laptop users and other folk who might want a quick
			way to put their computer onto the ethernet may want
			to use this. The driver was included with the default
			kernel source tree as of pl12 and possibly earlier.
			Bjorn Ekwall <[email-masked]> wrote the original.
			Expect about 80kb/s transfer speed from this via the
			parallel port. You should read the README.DLINK
			file in the kernel source tree. The latest release
			of this driver is v0.32, and it is included in the
			standard kernel of pl15

		DE-650
			Some people have been using this PCMCIA card for
			some time now with their notebooks. Note however,
			that using a PCMCIA card with Linux is not trivial.
			See the section on networking with a notebook for
			more information on PCMCIA cards. This driver is
			*not* part of the standard kernel.

		DE-100, DE-200, DE-220-T
			The manual says that it is 100% compatible with the
			NE2000. This is not true. You should call them and
			tell them you are using their card with Linux, and they
			should correct their documentation. Some pre-0.99pl12
			driver versions may have trouble recognizing the DE2**
			series as 16 bit cards, and these cards are the most
			widely reported as having the spurious transfer address
			mismatch errors. Note that there are cards from
			Digital (DEC) that are also named DE100 and DE200,
			but the similarity stops there.

	Unsupported:

		DE-620
			Same as the DE-600, only with two output formats.
			(BNC and RJ-45, I would assume... ????)
			Bjorn writes: "I have still no information on the
			DE-620 that I can include in this release. (Maybe
			someone well connected to D-Link sees this,
			hint, hint, hint...)

2.06 Cabletron

	Yes, another one of these companies that won't release its
	programming information. They waited for months before actually
	confirming that all their information was proprietary, deliberately
	wasting my time. Avoid their cards like the plague if you can.
	Also note that some people have phoned Cabletron, and have been
	told things like "a [email-masked] is working on a driver
	for linux" -- making it sound like I work for them. This is
	NOT the case. Anyway, if I were working for them, or even if
	I had signed a ND agreement, I wouldn't be able to tell
	everyone what a sleazy design the E2100 is. (See below.)

	If you feel like asking them why they don't want to release their
	info so that people can use their cards, write to [email-masked]
	Tell them that you are using Linux, and are disappointed that they
	don't support open systems. (See section 9.01)

	Supported: (...well, not *really* supported)

		E10**, E10**-x, E20**, E20**-x
			These are NEx000 almost-clones that are reported to
			work with the standard NEx000 drivers, thanks to a
			ctron-specific check during the probe. If there are
			any problems, they are unlikely to be fixed, as the
			programming information is unavailable.

		E21**
			Again, there is not much one can do when the
			programming information is proprietary.
			The E2100 is a poor design. Whenever it maps its
			shared memory in during a packet transfer, it
			maps it into the *whole 128K region*! That means you
			*can't* safely use another interrupt-driven shared
			memory device in that region, including another E2100.
			It will work _most_ of the time, but every once in
			a while it will bite you. (Yes, this problem can
			be avoided by turning off interrupts while
			transferring packets, but that will almost certainly
			lose clock ticks.

			Also, don't confuse the E2100 for a NE2100 clone.
			The E2100 is a shared memory NatSemi DP8390 design,
			roughly similar to a brain-damaged WD8013, whereas
			the NE2100 (and NE1500) use a bus-mastering AMD
			LANCE design.

			There is an alpha test driver available (even though
			I shouldn't have bothered) in the normal place
			(see the FAQ section) -- e2100.c -- let me know if
			you use it, and how it works. Don't forget to
			un-comment the line in config.in.

2.07	Allied Telesis

	Allied Telesis is the worlds largest maker of separate
	transceivers thanks to their low prices, and they now have a
	series of low-cost ethercards using the 79C960 version of the AMD
	LANCE. These are bus-master cards, and thus probably the fastest
	ISA bus ethercards available (although the 3c509 has lower latency
	thanks to predictive interrupts).

	Supported:

		AT1500
			The driver for the AT1500 series is new in the
			0.99pl12 kernel, but it won't work "out-of-the-box"
			with >16M machines. (NB This isn't a fundamental
			limitation, so stop pointing and laughing at the ISA
			bus. The driver just needs a hook to allocate
			low-memory buffers for the bus-master DMA, and should
			be just as fast on >16M systems. It can be easily
			fixed by initializing the LANCE driver with the
			character devices, but this fix depends on the
			resolution of the networking code uncertainty.)

			For the ISA bus master mode all structures used
			directly by the LANCE, the initialization block,
			Rx and Tx rings, and data buffers, must be accessible
			from the ISA bus, i.e. in the lower 16M of real memory.
			This is a problem for current Linux kernels on >16M
			machines. The network devices are initialized after
			memory initialization, and the kernel doles out memory
			from the top of memory downward. The current solution
			is to have a special network initialization routine
			that's called before memory initialization; this will
			eventually be generalized for all network devices.
			Low-memory "bounce-buffers" are used when needed.

			This driver should also work with NE1500 and NE2100
			clones.
			
			Future driver versions may figure out a way to
			autoDMA. Although there is no autoDMA (until I verify
			that autoDMA is safe and reliable), some versions
			(pl13) allow passing the DMA channel at boot-time via
			LILO. (Boot-time parameters can be made permanent in
			LILO v13+, read the docs.) The DMA channel otherwise
			defaults to DMA5.

			In pl14, there was a buglet that would hang some
			machines with AT1500 like cards. Either get pl15
			or newer, or go into ./init/main.c and move the
			sti(); and claibrate_delay(); (near line 366) in
			*front of* the #ifdef CONFIG_INET, instead of
			after it.
			
			Please report the exact chip used by your ethercard,
			and any success or failure you have. This driver is
			still young, and I've gotten few reports.

			More information on AMD LANCE based Ethernet cards
			can be found in section 5.08.

		AT1700
			The Allied Telesis AT1700 series ethercards are based
			on the Fujitsu MB86965. This chip uses a programmed
			I/O interface, and a pair of fixed-size transmit
			buffers. This allows small groups of packets to sent
			be sent back-to-back, with a short pause while
			switching buffers.
			
			A unique feature is the ability to drive 150ohm STP
			(Shielded Twisted Pair) cable commonly installed for
			Token Ring, in addition to 10baseT 100ohm UTP
			(unshielded twisted pair).
			
			A mis-feature to watch out for is that the current
			production version silently wires to DMA channel 5,
			rendering it useless. No device driver will be
			written using DMA if installing a second card into
			the machine breaks both, and the only way to disable
			the DMA is with a knife.
			
			The at1700 driver is included in the standard pl15
			kernel source tree.
			
2.08 Arcnet

	There is no Arcnet driver for Linux. Feel free to write a driver. With
	the very low cost and better performance of ethernet, I expect that
	most places will be giving away their Arcnet hardware for free,
	resulting in a lot of home systems with Arcnet.

	An advantage of Arcnet is that all of the cards have identical
	interfaces, so once a driver is available it will work for everyone.

2.09 Digital / DEC

	Supported: DE200, DE210, DE202, DE100, DEPCA rev E

		As of linux v1.0, there is a driver included as standard
		for these cards. It was written by David C. Davies.
		There is documentation included in the source file
		"depca.c", which includes info on how to use more than
		one of these cards in a machine.

		If you have / want to use the pl15 kernel or older,
		then you will have to use Peter Bauer's driver.
		It can be found as a separate patch called depca-0.8.tar.gz.
		You will have to un-comment the DEPCA line in "config.in"
		after installing the patch. You can find the patch on
		ftp.funet.fi, /pub/OS/Linux/BETA/depca/depca-0.8.tar.gz
		This version resets the card upon close so that you can
		use it with broken DOS drivers after a warm boot.

	Unsupported: Digital Etherlink III

		Peter Bauer said that "the new etherlink III seems to
		be a break: No official docu from DEC as far as today,
		other (incompatible??) hardware used, and (no joke) (at least
		for the first delivered cards) also a sharp knife necessary
		to get the card working (needs cut of some irq lines ...)
		As far as I know, lots of DEC Employees use Linux (at least
		for hobby purposes) and the depca-driver, because its a
		de-facto standard in DEC, so I encourage any DEC-employee
		reading this to check wether my writing is true, and to
		support sources of information about the etherworks-III."

2.10 Intel Ethernet Cards

	Supported: Ether Express

		This card uses the intel i82586. (Surprise, huh?)
		The driver is in the standard release of pl15.
		However, you will have to uncomment the line in
		"config.in" to use it. -- yes, this line is
		commented out for a reason. The driver is still
		in the testing phases, as of v1.0 as well.

		There is some technical information available on
		the i82586 in section 5.06, and also in the
		source code for the driver "eexpress.c". Don't
		be afraid to read it. ;-)

		The rason is that the driver works well with slow machines,
		but the i82586 occasionally hangs from the packet buffer
		contention that a fast machine can cause. I'll have
		to find a work-around before releasing the driver.
		One reported hack fix is to change all of the outw()
		calls to outw_p().

		If you do try the driver please post or send a report. 
		Include the kind of machine you are trying it with,
		and how heavily loaded your network is.

2.11 PureData

	Supported: PDUC8028, PDI8023

		The PureData PDUC8028 and PDI8023 series of cards are reported
		to work, thanks to special probe code contributed by Mike
		Jagdis <[email-masked]>. The support is integrated
		with the WD driver.

2.12 Xircom

	Another group that won't release documentation. No cards
	supported. Don't look for any support in the future unless
	they release their programming information. And this is
	highly unlikely, as they *forbid* you from even reverse-
	engineering their drivers. If you are already stuck with one,
	see if you can trade it off on some DOS (l)user. Read section
	9.01 if you are bored.

	And if you just want to verify that this is the case, you can
	reach Xircom at 1-800-874-7875 or +1-818-878-7600.

2.13 Zenith

	The built-in Z-Note network adaptor is based on the Intel
	i82593 using two DMA channels. There might be a driver for it
	in mid 1994. See section 5.06 for more information.
	Also note that the Z-Note is compatible with the IBM ThinkPad 300.

2.14 Racal-Interlan

	Note: I have been told that the following two drivers are 
	for patchlevel 11, and hence are a bit dated. The original
	author is Michael Hipp, and can be reached at the following addr:
		[email-masked]

	NI52**

	There is an alpha driver for the NI5210 floating about.
	(last seen on tsx-11.mit.edu /pub/linux/ALPHA/ni/ni52.tar.gz)
	This card also uses one of the Intel chips. See section
	5.06 for more information.

	NI65**

	There is also a driver for the LANCE based NI6510, and it
	can be found in the same place as the NI5210 driver above.
	I am not sure how much work it would be to hack the current
	LANCE driver in the kernel to support this card. If anyone
	has done so, let me know.

2.15 AMD LANCE (79C960)

	There really is no AMD ethernet card. You are probably reading this
	because the only markings you could find on your card said AMD
	and the above number. The above number refers to a chip from AMD
	that is the heart of many ethernet cards. See the section on the
	Allied Telesis AT1500, the NE1500/2100 and the information in
	section 5.08. Chances are that the existing LANCE driver will work
	with all AMD LANCE based cards. (...except perhaps the above
	mentioned NI6510 ???)
	
2.16 AT-Lan-Tec / RealTek Pocket adaptor

	This is a generic, low-cost OEM pocket adaptor being sold by
	AT-Lan-Tec, and (likely) a number of other suppliers. A
	driver for it is included in the standard pl15 kernel.
	Note that there is substantial information contained in the
	driver source file "atp.c" which presently lives in ./drivers/net/
	BTW, the adaptor (AEP-100L) has both 10baseT and BNC connections!
	You can reach AT-Lan-Tec at 1-301-948-7070. Ask for the model
	that works with Linux, or ask for "Vincent Bono" in tech support.
	In the Netherlands a compatible adaptor is sold under the name SHI-TEC
	PE-NET/CT, and sells for about $125. The vendor was Megasellers.
	They state that they do not sell to private persons, but I just
	gave them the name of my home institute. No questions asked.
	They are: Megasellers, Vianen, The Netherlands. They always
	advertise in Dutch computer magazines. In Germany, a similar
	adaptor comes as a no-brand-name product. Prolan 890b, no
	brand on the casing, only a roman II. Resellers can get a price
	of about $130, including a small wall transformer for the power.

	Physical Description

	The adaptor is "normal size" for the product class, about 57mm wide,
	22mm high tapering to 15mm high at the DB25 connector, and 105mm long
	(120mm including the BNC socket). It's switchable between the RJ45
	and BNC jacks with a small slide switch positioned between the two:
	a very intuitive design.

	It's powered by a lightweight 5V "wall brick" adaptor that terminates
	in a standard 5.0mm power connector. I measured an unconnected
	quiescent power draw of 102ma for BNC and 84ma for 10baseT. I hooked
	the pocket adaptor up to my home thinnet and started FTPing a large
	file. The power measurements were:

		idle, connected		99ma @ 5.1V
		active, connected	107ma @ 5.1V

	This was measured using a Fluke 8026B true-RMS multimeter, so I'm
	pretty confident the numbers are good. This power draw is low enough
	that you could buy or build a cable to take the 5V directly from the 	
	keyboard/mouse port available on many laptops. (Bonus points here
	for using a standardized power connector instead of proprietary one.)

2.17 Ansel

	Supported: AC3200 EISA
	
		This driver is not included in the pl15 kernel. To
		*alpha* test it, get the files ac3200.[c,h] from
		where you usually get alpha drivers (see the FAQ in
		this document if you dont know) and uncomment the
		line in config.in for the ac3200. If you use it,
		please let me know how things work out.

2.18 DFI

	Supported: DFINET-300 (NE1000) and DFINET-400 (NE2000)

		These cards are now detected (as of pl15) thanks to
		Eberhard Moenkeberg <[email-masked]> who noted that
		they use "DFI" in the first 3 bytes of the prom, instead
		of using 0x57 in bytes 14 and 15, which is what all the
		NE1000 and NE2000 cards use.

3. Clones of popular Ethernet cards.

	Due to the popular design of some cards, different companies will
	make "clones" or replicas of the original card. However, one must
	be careful, as some of these clones are not 100% compatible, and
	can be troublesome. Some common problems with "not-quite-clones"
	are noted in the question and answer section of this document.

	Also note that if your card isn't mentioned here, that really
	means nothing. Chances are that even if it is only a half decent
	clone of the original, then it will still work.

3.1 WD80x3 clones

	The following clones are reported to work with the standard
	WD80x3 driver:

	AT-LAN-TEC 8013
	PureData (not a 8013 clone, but the 8013 driver has special code)
	LANNET LEC-45
	PE-8013 (WD-8013 Compatible)

3.2 NE2000 clones

	The following clones are reported to work with the standard
	NE2000 driver:

	Accton NE2000 (might not get detected at boot, see section 6)
	Alta Combo NE2000 clone
	Aritsoft LANtastic AE-2 (OK, but has flawed error-reporting registers)
	Asante Etherpak 2001/2003
	AT-LAN-TEC NE2000 clone (uses Winbond chip that traps SCSI drivers)
	Cabletron products: E10**, E10**-x, E20**, E20**-x
	Cnet UTP 10baseT (NE 2000 emulation)
	D-Link Ethernet II (bad clones, but the driver checks for them)
	4-Dimension FD0490 EtherBoard16
	LTC E-NET/16 P/N: 8300-200-002 ([email-masked])
	Network Solutions HE-203
	SIIG Inc E-Lan/200 (NE 2000 comp.)
	SVEC 4 Dimension Ethernet

4. Cables, coax, twisted pairs etc.

	If you are starting a network from scratch, it's considerably less
	expensive to use thin ethernet, RG58 co-ax cable with BNC connectors,
	than old-fashioned thick ethernet, RG-5 cable with N connectors, or
	10baseT, twisted pair telco-style cables with RJ-45 eight wire "phone"
	connectors.

4.01 Thin Ethernet (thinnet)

	Thin ethernet is the "ether of choice". The cable is inexpensive. If
	you are making your own cables solid-core RG58A is $0.09/ft. and
	stranded RG58AU is $0.15/ft. Twist-on BNC connectors are < $2 ea.,
	and other misc. pieces are similarly inexpensive. It is essential
	that you properly terminate each end of the cable with 50 ohm
	terminators, so budget $2 ea. for a pair. It's also vital that
	your cable have no "stubs" -- the 'T' connectors must be attached
	directly to the ethercards. The only drawback is that if you have
	a big loop of machines connected together, and some bonehead breaks
	the loop by taking one cable off the side of his tee, the whole
	network goes down because it sees an infinite impedance (open
	circuit) instead of the required 50 ohm termination. Note that
	you can remove the tee piece from the card itself without killing
	the whole subnet, as long as you don't remove the cables from the
	tee itself. Of course this will disturb the machine that you
	pull the actual tee off of. 8-) And if you are doing a small
	network of two machines, you *still* need the tees and the 50 ohm
	terminators -- you *can't* just cable them together!

4.02 Twisted pair

	Twisted pair networks require active hubs, which start around $200,
	and the raw cable cost can actually be higher than thinnet. They are
	usually sold using the claim that you can use your existing telephone
	wiring, but it's a rare installation where that turns out to be the
	case. The claim that you can upgrade to higher speeds is also
	suspect, as most proposed schemes use higher-grade (read $$) cable and
	more sophisticated termination ($$$) than you would likely install on
	speculation. New gizmos are floating around which allow you to
	daisy-chain machines together, and the like. For example,
	Falleron sells EtherWave adaptors and transceivers. This device
	allows multiple 10baseT devices to be daisy-chained. They also
	sell a 3c509 clone that includes the EtherWave transceiver.
	The drawback is that it's more expensive and less reliable than a 
	cheap ($100-$150) mini-hub and another ethercard. IMO, you should
	either go for the hub approach or switch over to 10base2 thinnet.

	On the other hand, hubs are rapidly dropping in price, all 100Mb/sec
	ethernet proposals use twisted pair, and most new business
	installations use twisted pair. (This is probably to avoid the
	problem with idiots messing with the BNC's as described above.)

	If you are only connecting two machines, it is possible to avoid
	using a hub, by swapping the Rx and Tx pairs (1-2 and 3-6).

	Also, Russ Nelson adds that "New installations should use Category 5
	wiring. Anything else is a waste of your installer's time, as
	100Base-whatever is going to require Cat 5."

4.03 Thick Ethernet

	Thick ethernet is mostly obsolete, and is usually used only to remain
	compatible with an existing implementation. You can stretch the rules
	and connect short spans of thick and thin ethernet together with a
	passive $3 N-to-BNC connector, and that's often the best solution to
	expanding an existing thicknet. A correct (but expensive) solution is
	to use a repeater in this case.

	-- end of part 1 of 2 --
From: Paul Gortmaker <[email-masked]>
Newsgroups: comp.os.linux.announce,comp.os.linux.admin,comp.answers,news.answers
Subject: Linux Ethernet HOWTO (Part 2/2)
Keywords: Linux, Ethernet, TCP/IP, NET-2, network
Followup-To: poster
Approved: [email-masked] (Matt Welsh)

Archive-Name: linux/howto/ethernet/part2
Last-Modified: 16 Mar 1994

[This is part 2/2 of the Ethernet-HOWTO.]

5 Technical information.

	For those who want to play with the present drivers, or try to make
	up their own driver for a card that is presently unsupported, this
	information should be useful. If you do not fall into this category,
	then perhaps you will want to skip this section.

5.01 Probed addresses

	While trying to determine what ethernet card is there, the following
	addresses are autoprobed, assuming the type and specs of the card
	have not been set in the kernel. As of 0.99pl12, doing a "make config"
	will ask what cards are to be supported. The file names below are
	in /usr/src/linux/drivers/net/
	----------------------------------------------------------------
	wd.c:		0x300, 0x280, 0x380, 0x240
	3c501.c		0x280
	3c503.c:	0x300, 0x310, 0x330, 0x350, 0x250, 0x280, 0x2a0, 0x2e0
	3c507.c:	0x300, 0x320, 0x340, 0x280
	3c509.c:	<Special "ID Port" probe>
	at1700.c:	0x300, 0x280, 0x380, 0x320, 0x340, 0x260, 0x2a0, 0x240
	atp.c:		0x378, 0x278, 0x3bc
	depca.c		0x300, 0x200
	d_link.c:	0x378
	ne.c:		0x300, 0x280, 0x320, 0x340, 0x360
	hp.c:		0x300, 0x320, 0x340, 0x280, 0x2C0, 0x200, 0x240
	lance.c:	0x300, 0x320, 0x340, 0x360
	smc-ultra.c:	0x200, 0x220, 0x240, 0x280, 0x300, 0x340, 0x380
	eexpress.c:	0x300, 0x270, 0x320, 0x340
	3c509.c:	<Special "ID Port" probe>
	----------------------------------------------------------------
	There are some NE2000 clone ethercards out there that are waiting black
	holes for autoprobe drivers. While many NE2000 clones are
	safe until they are enabled, some can't be reset to a safe mode.
	These dangerous ethercards will hang any I/O access to their
	"dataports". The typical dangerous locations are:

	Ethercard jumpered base     Dangerous locations (base + 0x10 - 0x1f)
		0x300 *				0x310-0x317
		0x320				0x330-0x337
		0x340				0x350-0x357
		0x360				0x370-0x377

	* The 0x300 location is the traditional place to put an ethercard, but
	it's also a popular place to put other devices (often SCSI
	controllers). The 0x320 location is often the next one chosen, but
	that's bad for for the AHA1542 driver probe. The 0x360 location is
	bad, because it conflicts with the parallel port at 0x378.

	To avoid these lurking ethercard, here are the things you can do:

	o Probe for the device's BIOS in memory space. This is easy
	  and always safe, but it only works for cards that always have
	  BIOSes, like primary SCSI controllers.

	o Avoid probing any of the above locations until you think
	  you've located your device. The NE2000 clones have a reset range
	  from <base>+0x18 to <base>+0x1f that will read as 0xff, so probe
	  there first if possible. It's also safe to probe in the 8390
	  space at <base>+0x00 - <base>+0x0f, but that area will return
	  quasi-random values

	o If you must probe in the dangerous range, for instance if your
	  target device has only a few port locations, first check that
	  there isn't an NE2000 there. You can see how to do this by
	  looking at the probe code in /usr/src/linux/net/inet/ne.c

	In other news, I've written the code for the I/O port registrar.
	Peter MacDonald and I have been intensely discussing this, and I think
	our current scheme has the necessary functionality with minimal kernel
	size impact. (The implementation involved rewriting the bitmap ops in
	kernel/ioport.c:ioperm() so that most code could be shared.)

	Here is the current "blurb". As usual comments are welcome. Please
	keep them substantial and constructive (we've already talked about
	changing the name from "reserve=" to "noprobe=").

	==================

	Boot-Time Parameters: "reserve="
	
	In some machines it may be necessary to prevent device drivers from
	checking for devices (auto-probing) in a specific region. This may be
	because of poorly designed hardware that causes the boot to "freeze"
	(such as some ethercards), hardware that is mistakenly identified,
	hardware whose state is changed by an earlier probe, or merely
	hardware you don't want the kernel to initialize.

	The "reserve" boot-time argument addresses this problem by specifying
	an I/O port region that shouldn't be probed. That region is reserved
	in the kernel's port registration table as if a device has already
	been found in that region. Note that this mechanism shouldn't be
	necessary on most machine, only when there is a problem or special
	case.

	The boot-line syntax is

	  lilo-prompt: linux-image reserve=[<port>,<size>,<port>,<size>...]

	As usual with boot-time specifiers there is an 11 parameter limit, thus
	you can only specify 5 reserved regions per "reserve" keyword.
	Multiple "reserve" specifiers will work if you have an usually
	complicated request.

	If you specify a "reserve" region to protect a specific device, you
	must generally specify an explicit probe for that device. Most
	drivers ignore the port registration table if they are given an
	explicit address.

5.02 Skeleton / prototype driver

	OK. So you have decided that you want to write a driver for the
	Foobar Ethernet card, as you have the programming information,
	and it hasn't been done yet. (...these are the two main require-
	ments ;-) You can use the skeleton network driver that is provided
	with the Linux kernel source tree. It can be found in the file
	/usr/src/linux/drivers/net/skeleton.c as of 0.99pl15, and later.

	It's also very useful to look at the Crynwr (nee Clarkson) driver
	for your target ethercard, if it's available. Russ Nelson
	<[email-masked]> has been actively updating and writing these,
	and he has been very helpful with his code reviews of the current
	Linux drivers.

5.03 Driver interface to the kernel

	Here are some notes that may help when trying to figure out what
	the code in the driver segments is doing, or perhaps what it is
	supposed to be doing.

	=====================================================

	int ethif_init(struct device *dev)
	{
	    ...
		dev->send_packet = &ei_send_packet;
		dev->open = &ei_open;
		dev->stop = &ei_close;
		dev->hard_start_xmit = &ei_start_xmit;
		...
	}

	int ethif_init(struct device *dev)

	This function is put into the device structure in Space.c. It is
	called only at boot time, and returns '0' iff the ethercard 'dev'
	exists.

	=====================================================

	static int ei_open(struct device *dev)
	static int ei_close(struct device *dev)

	This routine opens and initializes the board in response to an
	socket ioctl() usually called by 'config' or 'ifconfig'. It is
	commonly stuffed into the 'struct device' by ethif_init().

	The inverse routine is ei_close(), which should shut down the
	ethercard, free the IRQs and DMA channels if the hardware permits,
	and turn off anything that will save power (like the transceiver).

	(Note: As of NET-2, the relevant program is '/etc/ifconfig' - and
	the device *can* be turned off or on via passing 'up' or 'down'
	to 'ifconfig' from the command line with the device name.)

	=====================================================

	static int ei_start_xmit(struct sk_buff *skb, struct device *dev)
		dev->hard_start_xmit = &ei_start_xmit;

	This routine puts packets to be transmitted into the hardware. It
	is usually stuffed into the 'struct device' by ethif_init().

	When the hardware can't accept additional packets it should set
	the dev->tbusy flag. When additional room is available, usually
	during a transmit-complete interrupt, dev->tbusy should be cleared
	and the higher levels informed with mark_bh(INET_BH).
	[[Note: pre0.99.4 kernels didn't use this interface for all packets.]]
	
	=====================================================

	...
	    if (dev_rint(buffer, length, is_skb ? IN_SKBUFF : 0, dev))
		   stats->rx_dropped++;
	...
	A received packet is passed to the higher levels using dev_rint().
	If the unadorned packet data in a memory buffer, dev_rint will copy
	it into a 'skbuff' for you. Otherwise a new skbuff should be
	kmalloc()ed, filled, and passed to dev_rint() with the IN_SKBUFF flag.

	=====================================================

5.04 Interrupts and Linux

	There are two kinds of interrupt handlers in Linux:
	fast ones and slow ones. You decide what kind you are installing by
	the flags you pass to irqaction(). The fast ones, such as the serial
	interrupt handler, run with _all_ interrupts disabled. The normal
	interrupt handlers, such as the one for ethercard drivers, runs with
	other interrupts enabled.

	There is a two-level interrupt structure. The "fast" part handles the
	device register, removes the packets, and perhaps sets a flag.  After
	it is done, and interrupts are re-enabled, the slow part is run if the
	flag is set.

	The flag between the two parts is set by:
		mark_bh(INET_BH);

	Usually this flag is set within dev_rint() during a received-packet
	interrupt, and set directly by the device driver during a
	transmit-complete interrupt.

	You might wonder why all interrupt handlers cannot run in
	"normal mode" with other interrupts enabled. Ross Biro uses this
	scenario to illustrate the problem:
		o You get a serial interrupt, and start processing it.
		  The serial interrupt is now masked.
		o You get a network interrupt, and you start transferring
		  a maximum-sized 1500 byte packet from the card.
		o Another character comes in, but this time the interrupts
		  are masked!

	The "fast" interrupt structure solves this problem by allowing
	bounded-time interrupt handlers to run without the risk of leaving
	their interrupt lines masked by another interrupt request.

	There is an additional distinction between fast and slow interrupt
	handlers -- the arguments passed to the handler. A "slow" handler is
	defined as

		static void
		handle_interrupt(int reg_ptr)
		{
		    int irq = -(((struct pt_regs *)reg_ptr)->orig_eax+2);
		    struct device *dev = irq2dev_map[irq];
		...

	While a fast handler gets the interrupt number directly

		static void
		handle_fast_interrupt(int irq)
		{
		...

	A final aspect of network performance is latency. The only board
	that really addresses this is the 3c509, which allows a predictive
	interrupt to be posted. It provides an interrupt response timer so
	that the driver can fine-tune how early an interrupt is generated.

	Alan Cox has some advice for anyone wanting to write drivers
	that are to be used with pl14 kernels and newer. He says:

	"Any driver intended for pl14 should use the new alloc_skb() and
	kfree_skbmem() functions rather than using kmalloc() to obtain an
	sk_buff. The new pl14 skeleton does this correctly. For drivers
	wishing to remain compatible with both sets the define
	'HAVE_ALLOC_SKB' indicates these functions must be used.

	In essence replace

		skb=(struct sk_buff *)kmalloc(size)
	with

		skb=alloc_skb(size)

	and

		kfree_s(skb,size)

	with

		kfree_skbmem(skb,size)	/* Only sk_buff memory though */

	Any questions should I guess be directed to me since I made the change.
	This is a change to allow tracking of sk_buff's and sanity checks on
	buffers and stack behaviour. If a driver produces the message
	'File: ??? Line: ??? passed a non skb!' then it is probable the
	driver is not using the new sk_buff allocators."

5.05 Programmed I/O vs. shared mem. vs. slave/master DMA

	Ethernet is 10Mbs. (Don't be pedantic, 3Mbs and 100Mbs don't count.)
	If you can already send and receive back-to-back packets, you just
	can't put more bits over the wire. Every modern ethercard can receive
	back-to-back packets. The Linux DP8390 drivers come pretty close to
	sending back-to-back packets (depending on the current interrupt
	latency) and the 3c509 and AT1500 hardware has no problem at all
	automatically sending back-to-back packets.

	The ISA bus can do 5.3MB/sec (42Mb/sec), which sounds like more than
	enough. You can use that bandwidth in several ways:

	Programmed I/O
	==============
	  Pro: Doesn't use any constrained system resources,
	       just a few I/O registers, and has no 16M limit.
	  Con: Usually the slowest transfer rate, the CPU is waiting
	       the whole time, and interleaved packet access is usually
	       difficult to impossible.

	Shared memory
	=============
	  Pro: Simple, faster than programmed I/O, and allows random
	       access to packets.
	  Con: Uses up memory space (a big one for DOS users, only a minor
	       issue under Linux), and it still ties up the CPU.

	Slave (normal) DMA
	==================
	  Pro: Frees up the CPU during the actual data transfer.
	  Con: Checking boundary conditions, allocating contiguous buffers,
	       and programming the DMA registers makes it the slowest
	       of all techniques.  It also uses up a scarce DMA
	       channel, and requires aligned low memory buffers.

	Master (bus-master) DMA
	=======================
	  Pro: Frees up the CPU during the data transfer, can string together
	       buffers, can require little or no CPU time lost on the
	       ISA bus.
	  Con: Requires low-memory buffers and a DMA channel. Any
	       bus-master will have problems with other bus-masters that
	       are bus-hogs, such as some primitive SCSI adaptors. A few
	       badly-designed motherboard chipsets have problems with
	       bus-masters. And a reason for not using *any* type of
	       DMA device is using a Cyrix 486 processor designed for
	       plug-in replacement of a 386: these processors must
	       flush their cache with each DMA cycle.

5.06 Programming the Intel chips (i82586 and i82593)

	These chips are used on a number of cards, namely the 3c507 ('86),
	the Intel EtherExpress 16 ('86), Microdyne's exos205t ('86),
	the Z-Note ('93), and the Racal-Interlan ni5210 ('86).

	Russ Nelson writes:
	"Most boards based on the 82586 can reuse quite a bit of their code.
	More, in fact, than the 8390-based adapters. There are only three
	differences between them:

	  o The code to get the Ethernet address,
	  o The code to trigger CA on the 82586, and
	  o The code to reset the 82586.

	The Intel EtherExpress 16 is an exception, as it I/O maps the 82586.
	Yes, I/O maps it. Fairly clunky, but it works.

	Garrett Wollman did an AT&T driver for BSD that uses the BSD
	copyright. The latest version I have (Sep '92) only uses a single
	transmit buffer. You can and should do better than this if you've
	got the memory. The AT&T and 3c507 adapters do; the ni5210 doesn't.

	The people at Intel gave me a very big clue on how you queue up
	multiple transmit packets. You set up a list of
	NOP->XMIT->NOP->XMIT->NOP->XMIT->(beginning) blocks, then you set the
	"next" pointer of all the NOP blocks to themselves. Now you start
	the command unit on this chain. It continually processes the first
	NOP block. To transmit a packet, you stuff it into the next transmit
	block, then point the NOP to it. To transmit the next packet, you
	stuff the next transmit block and point the previous NOP to *it*. In
	this way, you don't have to wait for the previous transmit to finish,
	you can queue up multiple packets without any ambiguity as to whether
	it got accepted, and you can avoid the command unit start-up delay."

5.07	Technical information from 3Com

	From: Cameron Spitzer 764-6339 <[email-masked]>
	Subject: getting 3Com Adapter manuals
	Date: Mon, 27 Sep 1993 21:17:07 +0200
	
	Since this is becoming a FAQ, I'm going to tread the thin
	ice of No Commercial Use and answer it here.

	3Com's Ethernet Adapters are documented for driver writers
	in our "Technical References" (TRs). These manuals describe
	the programmer interfaces to the boards but they don't talk
	about the diagnostics, installation programs, etc that end
	users can see.
	
	The Network Adapter Division marketing department has the
	TRs to give away. To keep this program efficient, we
	centralized it in a thing called "CardFacts." CardFacts is
	an automated phone system. You call it with a touch-tone
	phone and it faxes you stuff. To get a TR, call CardFacts
	at 408-727-7021. Ask it for Developer's Order Form,
	document number 9070. Have your fax number ready when you
	call. Fill out the order form and fax it to 408-764-5004.
	Manuals are shipped by Federal Express 2nd Day Service.
	
	If you don't have a fax and nobody you know has a fax,
	really and truly, *then* send mail to
	[email-masked] and tell her about your problem.
	PLEASE use the fax thing if you possibly can.
	
	After you get a manual, if you still can't figure out how to
	program the board, try our "CardBoard" BBS at
	1-800-876-3266, and if you can't do that, write
	[email-masked] and ask him for alternatives. If
	you have a real stumper that nobody has figured out yet, the
	fellow who needs to know about it is
	[email-masked].
	
	There are people here who think we are too free with the
	manuals, and they are looking for evidence that the system
	is too expensive, or takes too much time and effort. That's
	why it's important to try to use CardFacts *before* you
	start calling and mailing the people I named here.
	
	There are even people who think we should be like Diamond
	and Xircom, requiring tight "partnership" with driver
	writers to prevent poorly performing drivers from getting
	written. So far, 3Com customers have been really good about
	this, and there's no problem with the level of requests
	we've been getting. We need your continued cooperation and
	restraint to keep it that way.
	
	Cameron Spitzer, 408-764-6339
	3Com NAD
	Santa Clara
	work: [email-masked]
	home: [email-masked]

5.08 Notes on AMD PCnet-ISA / LANCE Based cards (79C960)

	The AMD LANCE (Local Area Network Controller for Ethernet)
	was the original offering, and has since been replaced by
	the "PCnet-ISA" chip, otherwise known as the 79C960.
	A relatively new chip from AMD, the 79C960, is the heart of many
	new cards being released at present. Note that the name "LANCE"
	has stuck, and some people will refer to the new chip by the old
	name. Dave Roberts of the Network Products Division of AMD was kind
	enough to contribute the following information regarding this chip:

	"As for the architecture itself, AMD developed it originally
	and reduced it to a single chip -- the PCnet(tm)-ISA -- over a year
	ago. It's been selling like hotcakes ever since.

	Functionally, it is equivalent to a NE1500. The register set
	is identical to the old LANCE with the 1500/2100 architecture
	additions. Older 1500/2100 drivers will work on the PCnet-ISA.
	The NE1500 and NE2100 architecture is basically the same.
	Initially Novell called it the 2100, but then tried to distinguish
	between coax and 10BASE-T cards. Anything that was 10BASE-T only was
	to be numbered in the 1500 range. That's the only difference.

	Many companies offer PCnet-ISA based products, including HP,
	Racal-Datacom, Allied Telesis, Boca Research, Kingston Technology, etc.
	The cards are basically the same except that some manufacturers
	have added "jumperless" features that allow the card to
	be configured in software. Most have not. AMD offers a standard
	design package for a card that uses the PCnet-ISA and many
	manufacturers use our design without change.
	What this means is that anybody who wants to write drivers for
	most PCnet-ISA based cards can just get the data-sheet from AMD. Call
	our literature distribution center at (800)222-9323 and ask for the
	Am79C960, PCnet-ISA data sheet. It's free.

	A quick way to understand whether the card is a "stock" card
	is to just look at it. If it's stock, it should just have one large
	chip on it, a crystal, a small IEEE address PROM, possibly a socket
	for a boot ROM, and a connector (1, 2, or 3, depending on the media
	options offered). Note that if it's a coax card, it will have some
	transceiver stuff built onto it as well, but that should be near the
	connector and away from the PCnet-ISA.

	The PCnet-ISA is faster than the original LANCE design and
	makes better use of the available bus bandwidth. Additionally, some
	LANCE bugs were corrected and many enhancements were made."

	There is also some info regarding the LANCE chip in the file
	lance.c which is included in the standard kernel.

5.09 Multicast and Promiscuous mode

	One of the things I've been working on recently is the
	major remaining item on the ethercard feature list:
	implementing multicast and promiscuous mode hooks.
	
	At first I was planning to do it while implementing either
	the /dev/* or DDI interface, but that's not really the
	correct way to do it. We should only enable multicast or
	promiscuous modes when something wants to look at the
	packets, and shut it down when that application is
	finished, neither of which is strongly related to when the
	hardware is opened or released.
	
	I'll start by discussing promiscuous mode, which is
	conceptually easy to implement. For most hardware you
	only have to set a register bit, and from then on you get
	every packet on the wire. Well, it's almost that easy;
	for some hardware you have to shut the board (potentially
	dropping a few packet), reconfigure it, and then re-enable
	the ethercard. This is grungy and risky, but the
	alternative seems to be to have every application register
	before you open the ethercard at boot-time.
	
	OK, so that's easy, so I'll move on something that's not
	quite so obvious: Multicast. It can be done two ways:
	
	1) Use promiscuous mode, and a packet filter like the
	   Berkeley packet filter (BPF). The BPF is a pattern matching
	   stack language, where you write a program that picks out the
	   addresses you are interested in. Its advantage is that it's
	   very general and programmable. Its disadvantage is that there
	   is no general way for the kernel to avoid turning on promiscuous
	   mode and running every packet on the wire through every registered
	   packet filter. See the next section for more information on BPF.
	
	2) Using the built-in multicast filter that most etherchips have.
	
	I guess I should list what a few ethercards/chips provide:
	
	Chip/card  Promiscuous	Multicast filter
	========================================
	Seeq8001/3c501	Yes	Binary filter (1)
	3Com/3c509	Yes	Binary filter (1)
	8390		Yes	Autodin II six bit hash (2) (3)
	LANCE		Yes	Autodin II six bit hash (2) (3)
	i82586		Yes	Hidden Autodin II six bit hash (2) (4)

	(1) These cards claim to have a filter, but it's a simple
	yes/no 'accept all multicast packets', or 'accept no
	multicast packets'.
	
	(2) AUTODIN II is the standard ethernet CRC (checksum)
	polynomial. In this scheme multicast addresses are hashed
	and looked up in a hash table. If the corresponding bit
	is enabled, this packet is accepted. Ethernet packets are
	laid out so that the hardware to do this is trivial -- you
	just latch six (usually) bits from the CRC circuit (needed
	anyway for error checking) after the first six octets (the
	destination address), and use them as an index into the
	hash table (six bits == a 64-bit table).
	
	(3) These chips use the six bit hash, and must have the
	table computed and loaded by the host. This means the
	kernel must include the CRC code.
	
	(4) The 82586 uses the six bit hash internally, but it
	computes the hash table itself from a list of multicast
	addresses to accept.

	Note that none of these chips do perfect filtering, and we
	still need a middle-level module to do the final
	filtering. Also note that in every case we must keep a
	complete list of accepted multicast addresses to recompute
	the hash table when it changes.
	
	My first pass at device-level support is detailed in the
	new outline driver skeleton.c (pl14 and up.)

	It looks like the following:
	
	#ifdef HAVE_MULTICAST
	static void set_multicast_list(struct device *dev, int num_addrs,
					 void *addrs);
	#endif
	.
	.
	
	ethercard_open() {
	...
#ifdef HAVE_MULTICAST
		dev->set_multicast_list = &set_multicast_list;
	#endif
	...
	
	#ifdef HAVE_MULTICAST
	/* Set or clear the multicast filter for this adaptor.
	   num_addrs == -1	Promiscuous mode, receive all packets
	   num_addrs == 0	Normal mode, clear multicast list
	   num_addrs > 0	Multicast mode, receive normal and
				MC packets, and do best-effort filtering.
	 */
	static void
	set_multicast_list(struct device *dev, int num_addrs, void *addrs)
	{
	...

	Any comments, criticism, etc. are welcome.

	Alan Cox adds that "...in pl14, user programs can access promiscuous
	mode but not multicast mode, even though the drivers support both.
	The ifconfig program allows you to mark an interface 'promisc'."
	
5.10 The Berkeley Packet Filter (BPF)

	I'm not bitterly opposed to it, but I'm coming to the
	conclusion that the 'bpf' functionality should not be provided
	by the kernel, but should be in a (hopefully little-used)
	compatibility library.
	
	For those not in the know: 'bpf' (the Berkeley Packet Filter)
	is an mechanism for specifying to the kernel networking layers
	what packets you are interested in. It's implemented as a
	specialized stack language interpreter built into a low level
	of the networking code. An application passes a program
	written in this language to the kernel, and the kernel runs the
	program on each incoming packet. If the kernel has multiple
	'bpf' applications, each program is run on each packet.
	
	The problem is that it's difficult to deduce what kind of
	packets the application is really interested in from the packet
	filter program, so the general solution is to always run the
	filter. Imagine a program that registers a 'bpf' program to
	pick up a low data-rate stream sent to a multicast address.
	Most ethernet cards have a hardware multicast address filter
	implemented as a 64 entry hash table that ignores most unwanted
	multicast packets, so the capability exists to make this a very
	inexpensive operation. But with the BFP the kernel must switch
	the interface to promiscuous mode, receive _all_ packets, and
	run them through this filter. This is work, BTW, that's very
	difficult to account back to the process requesting the packets.

5.11 Unresolved questions / concerns

	There may be some benefit from processing packet data as it is
	transferred to and from the ethercard, especially with very fast
	processors transferring data to a slow ethercard. As I see it this
	question has multiple parts:
		1) Is there any useful processing power available, perhaps
		   during the ISA bus recovery period, or while the 8390
		   remote DMA is preparing for another transfer??
		2) Is there any useful but simple work that can be done
		   between/during each word of the copy, such as calculating
		   a CRC, or discarding obviously unwanted packets??
		3) would the complexity of an interface to do this make future
		   ethercard drivers impossible??

	There should be a better structure than Space.c - Drivers should be
	able to autoprobe for all installed ethercards rather than just
	quitting after finding the first.  I've written code to do this,
	but the constant promise (threat?) of DDI has prevented me from
	making it standard.

	A related topic is the problem of driver probes corrupting
	unrelated hardware. Even worse is a probe into a dataport that
	isn't set up to transfer data, which will freeze the machine. The
	common suggestion is a boot-time device registry that records
	already-used I/O ports and shared memory. This has been implemented
	as of pl13, see section 5.01.

6 Possible problems, and troubleshooting.

	This section tries to answer any unresolved questions, and not so
	common solutions to common problems. They are sorted on a "per
	manufacturer basis". You should have also read the relevant info.
	from section 1 about your specific card. Section 8 contains more
	general FAQ's.

6.01 Problems with NE2000 (and clones)

	"DMA address mismatch"
	======================

	Is the chip a real NatSemi 8390? (DP8390, DP83901, DP83902 or DP83905)?
	If not, some clone chips don't correctly implement the transfer
	verification register. MS-DOS drivers never do error checking,
	so it doesn't matter to them.

	Are most of the messages off by a factor of 2?
	If so:	Are you using the NE2000 in a 16 bit slot?
		Is it jumpered to use only 8 bit transfers?

	The Linux driver expects a NE2000 to be a 16 bit slot. A NE1000 can
	be in either size slot. This problem can also occur with some clones,
	notably D-Link 16 bit cards, that don't have the correct ID bytes
	in the station address PROM. [[ This should be fixed in pl12.]]

	Are you running the bus faster than 8Mhz?
	If you can change the speed (faster or slower), see if that
	makes a difference. Most NE2000 clones will run at 16Mhz, but
	some may not. Changing speed can also mask a noisy bus.

	What other devices are on the bus?
	If moving the devices around changes the reliability, then you
	have a bus noise problem -- just what that error message was
	designed to detect. Congratulations, you've probably found the
	source of other problems as well.

	Machine Hangs during Boot.
	==========================

	Problem:  The machine hangs during boot right after the "8390..."  or
		  "WD...." message. Removing the NE2000 fixes the problem.

	Solution: Change your NE2000 base address to 0x360 (or 0x340 for
		  pl12 or later kernels.) Alternatively, you can use the new
		  device registrar implemented in pl13 (see section 5.1)

	Reason:   Your NE2000 clone isn't a good enough clone. An active
		  NE2000 is a bottomless pit that will trap any driver
		  autoprobing in its space. The other ethercard drivers take
		  great pain to reset the NE2000 so that it's safe, but some
		  clones cannot be reset. Clone chips to watch out for:
		  Winbond 83C901. Changing the NE2000 to a less-popular
		  address will move it out of the way of other autoprobes,
		  allowing your machine to boot.

	Problem:  The machine hangs during the SCSI probe at boot.

	Solution: It's the same problem as above, change the
		  ethercard's address, or use the device registrar.

	Problem:  The machine hangs during the soundcard probe at boot.

	Solution: No, that's really during the silent SCSI probe, and it's
		  the same problem as above.

	"eth0: DMAing conflict in ne_block_input"
	=========================================

	This bug came from timer-based packet retransmissions. If you got a
	timer tick _during_ a ethercard RX interrupt, and timer tick tried to
	retransmit a timed-out packet, you could get a conflict. Because of
	the design of the NE2000 you would have the machine hang (exactly the
	same the NE2000-clone boot hangs).

	Early versions of the driver disabled interrupts for a long time,
	and didn't have this problem. Later versions are fixed. (ie. kernels
	after 0.99p9 should be OK.)

	NE2000 not detected at boot.
	============================

	A few people have reported a problem with detecting the Accton NE2000.
	This problem occurs only at boot-time, and the card is later detected
	at run-time by the identical code my (alpha-test) ne2k diagnostic
	program. Accton has been very responsive, but I still haven't tracked
	down what is going on. I've been unable to reproduce this problem
	with the Accton cards we purchased. If you are having this problem,
	please send me an immediate bug report. For that matter, if you have
	an Accton card send me a success report, including the type of the
	motherboard. I'm especially interested in finding out if this problem
	moves with the particular ethercard, or stays with the motherboard.
	
	Here are some things to try, as they have fixed it for some people:
	1) Change the bus speed, or just move the card to a different slot (!).
	2) Change the "I/O recovery time" parameter in the BIOS
	   chipset configuration.
	3) Make the following code change suggested by David Cutler,
	   <[email-masked]> to ne.c around line 150:

	    for(i = 0; i < 32 /*sizeof(SA_prom)*/; i+=2) {
	-        SA_prom[i] = inb_p(ioaddr + NE_DATAPORT);
	-        SA_prom[i+1] = inb_p(ioaddr + NE_DATAPORT);
	+        SA_prom[i] = inb(ioaddr + NE_DATAPORT);
	+        SA_prom[i+1] = inb(ioaddr + NE_DATAPORT);
	        if (SA_prom[i] != SA_prom[i+1])
	            wordlength = 1;
	    }

	Yes, this removes the delay between board accesses, something that
	would normally increase the likelihood of data corruption rather
	than decreasing it. Note that this change is already incorporated
	into pl15. If you have an older kernel, you may have to do it
	yourself.

6.02 Problems with WD80*3 cards

	Detected Non-existent Ethercard
	===============================

	Problem:  A WD80*3 is falsely detected. Removing the sound or
		  MIDI card eliminates the "detected" message.

	Solution: Update your ethercard driver: new versions include an
		  additional sanity check.

	Reason:   Some MIDI ports happen to produce the same checksum as a
		  WD ethercard.

	Error messages from the 80*3
	============================

	Problem:  You get messages such as the following with your 80*3:
			eth0: bogus packet size, status = ........
			kmalloc called with impossibly large argument (65400)
			eth0: Couldn't allocate sk_buff of size 65400
			eth0: receiver overrun

	Reason:   There is a shared memory problem.

	Solution: If the problem is sporadic, you have hardware problems.
		  Typical problems that are easy to fix are board conflicts,
		  having cache or "shadow ROM" enabled for that region, or
		  running your bus faster than 8Mhz. There are also a
		  surprising number of memory failures on ethernet cards,
		  so run a diagnostic program if you have one for your
		  ethercard.

		  If the problem is continual, and you have have to reboot
		  to fix the problem, record the boot-time probe message
		  and mail it to [email-masked] - Take particular note of
		  the shared memory location.

	Will not detect my 80x3
	=======================

	Reason:   The Mitsumi CD-ROM (mcd) driver probe at 0x300 will
		  succeed if just about *anything* is that I/O location.
		  This is bad news and needs to be a bit more robust. (pl15)
		  Once another driver registers that it "owns" an I/O
		  location, other drivers (incl. the wd80x3) are "locked
		  out" and can not probe that addr for a card.

	Solution: Recompile a new kernel without any excess drivers that
		  you aren't using, including the above mcd driver.
		  Or try moving your ethercard to a new I/O addr. Valid
		  I/O addr. for all the cards are listed in section 5.1
		  You can also point the mcd driver off in another direction
		  by a boot-time parameter (via LILO) such as:
			"mcd=0x200,12"

6.03 Problems with 3Com cards

	Choosing the Interrupt of the 3c503
	===================================

	Problem:  The 3c503 picks IRQ n at boot, but this is needed for some
		  other device which needs IRQ n. (eg. CD ROM driver, etc.)
		  Can this be fixed without compiling this into the kernel?

	Solution: The 3c503 driver probes for a free IRQ line in the order
		  {5, 9/2, 3, 4}, and it should pick a line which isn't being
		  used. The pre-pl12 (SLS 1.02) driver picked the IRQ line
		  at boot-time, and the current driver (pl12) chooses when
		  the card is open()/'ifconfig'ed. Note the "bug" noted in
		  the 3c503 section in 1.01

		  Alternately, you can fix the IRQ at boot by passing
		  parameters via LILO. The following selects IRQ9, base
		  location 0x300, <ignored value>, and if_port #1 (the
		  external transceiver).
			lilo: linux ether=9,0x300,0,1,eth0

		  The following selects IRQ3, probes for the base location,
		  <ignored value>, and the default if_port #0 (the internal
		  transceiver)
			lilo: linux ether=3,0,0,0,eth0

	"3c503: Configured interrupt number XX is out of range."
	========================================================

	Problem:  Whoever built your kernel fixed the ethercard IRQ at XX.

	Reason:   The above is truly evil, and worse than that, it is
		  not necessary. The 3c503 will autoIRQ when it gets
		  "ifconfig"ed, and pick one of IRQ{5, 2/9, 3, 4}.

	Solution: Use lilo to set the IRQ, or rebuild the kernel, enabling
		  autoIRQ by not specifying the IRQ line.

	Choosing the output of the 3c503
	================================

	Problem:  The supplied 3c503 drivers don't use the AUI (thicknet) port.
		  How does one choose it over the default thinnet port?

	Solution: The 3c503 AUI port can be selected at boot-time with 0.99pl12
		  and later. The selection is overloaded onto the low bit of
		  the currently-unused dev->rmem_start variable, so a boot-time
		  parameter of:
			lilo: linux ether=0,0,0,1,eth0
		  should work. A boot line to force IRQ 5, port base 0x300,
		  and use an external transceiver is:
			lilo: linux ether=5,0x300,0,1,eth0

7 Networking with a laptop computer

	There are currently only a few ways to put your laptop on a network.
	You can use the SLIP code (and run at serial line speeds);
	you can buy one of the few laptops that come with a NE2000-compatible
	ethercard or PCMCIA slot built-in; you can get a laptop with a
	docking station and plug in an ISA ethercard; or you can use a
	parallel port Ethernet adapter such as the D-Link DE-600.

7.01 Option 1 -- using SLIP

	This is the cheapest solution, but by far the most difficult. Also,
	you will not get very high transmission rates. Since SLIP is not
	really related to ethernet cards, it will not be discussed further
	here. See the NET-2 HOWTO.

7.02 Option 2 -- Built in NE2000 compatible or PCMCIA Ethercard.

	The second solution severely limits your laptop choices and is fairly
	expensive. Be sure to read the specifications carefully, you may find
	that you will have to buy an additional non-standard transceiver to
	actually put the machine on a network.

	As this area of Linux development is fairly young, I'd suggest
	that you join the LAPTOPS mailing channel. See section 0.02
	which describes how to join a mailing list channel. Try and
	determine exactly what hardware you have (ie. card manufacturer,
	PCMCIA chip controller manufacturer) and then ask on the LAPTOPS
	channel. Regardless, don't expect things to be all that simple.
	Expect to have to fiddle around a bit, and patch kernels, etc.
	Maybe someday you will be able to type "make config" 8-)

	There is a number of programs on tsx-11.mit.edu in
	/pub/linux/packages/laptops/ that you may find useful. These
	range from PCMCIA Ethercard drivers to programs that communicate
	with the PCMCIA controller chip. Note that these drivers are
	usually tied to a specific PCMCIA chip (ie. the intel 82365
	or the TCIC/2) On a brighter note, I know that people have used the
	Linksys/D-Link 650 PCMCIA Ethernet PC Card with both controller
	chipsets, so it *can* be done. I have also seen reports of
	people using the IBM Credit Card Adapter for Ethernet with the
	intel 82365 chip. This is all just from following the LAPTOPS
	channel.

	The 3c589 from 3Com is supposed to look a lot like a 3c509.

	Anyway, the PCMCIA driver problem isn't specific to the Linux world.
	It's been a real disaster in the MS-DOS world. In that world
	people expect the hardware to work if they just follow the manual.
	They might not expect it to interoperate with any other hardware
	or software, or operate optimally, but they do expect that the
	software shipped with the product will function. Many PCMCIA
	adaptors don't pass this test.

7.03 Option 3 -- ISA Ethercard in the Docking Station.

	I recommend the third solution. Docking stations for laptops typically
	cost about $250 and provide two full-size ISA slots, two serial and one
	parallel port. Most (all?) docking stations are powered off of the
	laptop's batteries, and a few allow adding extra batteries in the
	docking station if you use short ISA cards. You can add an inexpensive
	ethercard and enjoy full-speed ethernet performance.

7.04 Option 4 -- Pocket / parallel port adaptors.

	The "pocket" ethernet adaptors may also fit your need.
	Until recently they actually costed more than a docking station and
	cheap ethercard, and most tie you down with a wall-brick power supply.
	At present, you can choose from the D-Link, or the RealTek adaptor.
	Most other companies, especially Xircom, treat the programming
	information as a trade secret, so support will likely be slow in
	coming.

	You can sometimes avoid the wall-brick with the adaptors by buying
	or making a cable that draws power from the laptop's keyboard
	port. (This is mentioned in the info. for the AT-Lan-Tec unit.)

	The keyboard pinouts (5 pin DIN) are as follows:

		Signal/Function			Pin #
		---------------			-----
		KEYCLK (clock)			1
		KEYDAT (data)			2
		N/C				3
		Ground				4
		+5 V				5

	A quick check with a voltmeter will verify which pins are 4 and 5
	if you are not sure.
8 Frequently asked questions

	Here are some of the more frequently asked questions about using
	Linux with an Ethernet connection. Some of the more specific
	questions are sorted on a "per manufacturer basis" and are listed
	in the "Troubleshooting" section. (section 6). However, since this
	document is basically "old" by the time you get it, any "new" problems
	will not appear here instantly. For these, I suggest that you make
	efficient use of your newsreader. For example, nn users would type
		nn -xX -s'3c'
	to get all the news articles in your subscribed list that have
	"3c" in the subject. (ie. 3com, 3c509, 3c503, etc.)
	The moral: Read the man page for your newsreader.
	
8.01 Just the FAQ's ma'am -- just the FAQ's.

	Q: I heard that there is an alpha driver available for my card.
	   Where can I get it?

	A: Assuming that it is a djb driver, it will be on ftp.super.org
	   in the /pub/linux/ area. Things change here quite frequently,
	   so just look around for it. There is usually only about 3
	   subdirs, so you should be able to find it. Now, if it really
	   is an alpha, or pre-alpha driver, then please treat it as
	   such. In other words, don't complain because you can't figure
	   out what to do with it. If you can't figure out how to install
	   it, then you probably shouldn't be testing it. Also, if it brings
	   your machine down, don't complain. Instead, send us a well
	   documented bug report, or even better, a patch!

	Q: Is there token ring support for Linux?

	A: No, there is no token ring support in Linux. To support token ring
	   requires more than only a writing a device driver, it also requires
	   writing the source routing routines for token ring. Given that
	   token ring is expensive, not fast, and will probably be swept away
	   by 100baseVG in a few months, it doesn't seem worth it to write
	   a driver. In case anyone wants to, I looked at writing a token ring
	   device driver, and concluded that the hardware interface
	   wasn't too difficult to do, but writing the support for source
	   routing would take significantly longer than I was willing to spend
	   on an expensive and dying technology.

	   Alan Cox adds: "It will require [...] changes to the bottom socket
	   layer to support 802.2 and 802.2 based TCP/IP. Don't expect
	   anything soon."

	Q: Is there FDDI support for Linux?

	A: No, there is no Linux driver for any FDDI boards. I come from a
	   place with supercomputers, so an external observer might think
	   FDDI would be high on my list. But FDDI never delivered end-to-end
	   throughput that would justify its cost, and it seems to be a nearly
	   abandoned technology now that 100base{X,Anynet} seems imminent.
	   (And yes, I know you can now get FDDI boards for <$1K. That
	   seems to be a last-ditch effort to get some return on the
	   development investment. Where is the next generation of FDDI
	   going to come from?)

	Q: Can I link 10BaseT (RJ45) based systems together without a hub?

	A: You can link 2 machines easily, but no more than that, without
	   extra devices/gizmos. See section 4 on wiring -- it explains
	   how to do it. And no, you can't hack together a hub just by
	   crossing a few wires and stuff. It's pretty much impossible 
	   to do the collision signal right without duplicating a hub.

	Q: Is there IPX or Novell support available for Linux?

	A: Alan Cox writes: "The novell protocols are available from novell
	   for various amounts. IPX is freely documented. SPX is about $1000
	   but I'm told Xerox SPP is identical. _PLEASE_ has anyone got any
	   freely distributable Xerox SPP code/documentation? The novell
	   server spec costs you $15000 + royalties providing you only
	   want to write a client, or $30000 + royalties otherwise. Needless
	   to say the final output has to be binary only and subject to a
	   novell license. Reading their license rules by my interpretation
	   its also impossible for us to do because you would seem to have
	   to bar disassembly of your final result, which is not allowed
	   in the EEC.

	   Bits of NCP are known, and I hope eventually enough will be known
	   to write limited NCP support into Linux, for the moment I'm poking
	   around at IPX, tho this will have to wait until the new network
	   code is finished.

	   An Alpha test IPX protocol layer is available from me (Alan)
	   for pl14 or higher. People are also exploring the issue of NCP and
	   the new Dr Dobbs journal article on the innards of netware has
	   provided a core of good information."

	   As an alternative, Miquel van Smoorenburg suggests the following:
	   "It _is_ possible to set up a dedicated PC running both novell and
	   the PD SOSS server and let it gateway from NFS to novell. This way
	   it is possible to mount the Novell drives on the Unix client.

	   SOSS is a PD (perhaps with some restrictions, but freely available)
	   NFS server for DOS. It includes the PC/IP TCP/IP implementation
	   and runs on a packet driver. I have run both a Novell client
	   (with PDIPX, a Packet Driver IPX) and this SOSS server together
	   successfully."

	   You can get "Stan's Own Server System" from the following location:
		hilbert.wharton.upenn.edu:pub/tcpip/soss.zip
	   Note that this version has the IP bugs fixed and the subdirs
	   with extensions bug fixed. Some of the soss.zoo archives do
	   not contain these fixes.

	Q: What needs to be done so that Linux can run two ethernet cards?

	A: The easiest solution is to get 0.99pl13 or newer, as the hooks for
	   multiple ethercards are all there.
	   You can enable additional ethercards with LILO parameters such as:

		lilo: linux ether=5,0x300,0,1,eth0 ether=15,0x280,eth1

	   These boot time arguments can be made permanent so that you
	   don't have to re-enter them every time. See the LILO manual.

	Q: Okay, I can run 2 cards -- can I run Linux as a gateway 
	   between two networks?

	A: This is really a question for the NET-HOWTO, but it is 
	   answered here anyways: Charles Hedrick (aka Mr. Slip)
	   had this to say:

	   "Yes, however I'm a bit nervous about doing it. The problem isn't
	   functionality -- there's IP forwarding code, and as far as I know,
	   it works. Some people do use it. However routers need to be
	   particularly careful to avoid creating network problems such as
	   "meltdowns." The Linux IP layer doesn't have quite enough of these
	   protective features. It will only cause trouble if other hosts on
	   your network are misconfigured, and even then it probably won't
	   cause much trouble (assuming that only systems actually acting as
	   gateways are built with IP_FORWARD enabled). But I'd still rather
	   use a router that met all of the requirements of the host and
	   router requirements in the RFC's. (Note that not all other Unix
	   implementations do either. I'm concerned about things like not
	   sending ICMP responses to messages that arrive as media 
	   broadcasts. 386BSD looks OK, but older BSD-based implementations
	   often didn't do all of these checks.)

	   It depends a lot on what the network is like and how critical it is.
	   For a home setup with a couple of hosts, I see no problem at all.
	   But I would not consider using Linux as a router on a large
	   campus network at the moment. I still think that by release 1.0,
	   Linux will be a reasonably well-behaved host. But I think use
	   as a router in critical situations should wait until somebody
	   has checked the ip and icmp modules for compliance with RFC 1009
	   and a few other specs."

	Q: I have /dev/eth0 as a link to /dev/xxx. Is this right?

	A: Contrary to what you have heard, the files in /dev/* are not used.
	   I originally thought that they might be an OK idea. I've since
	   concluded that they won't work, at least in the documented form.

	Q: Should I disable trailers when I "ifconfig" my ethercard?

	A: You can't disable trailers, and you shouldn't want to.
	   'Trailers' are a hack to avoid data copying in the
	   networking layers. The idea was to use a trivial 
	   fixed-size header of size 'H', put the variable-size header 
	   info at the end of the packet, and allocate all packets
	   'H' bytes before the start of a page. While it was a good
	   idea, it turned out to not work well in practice.
	   If someone suggests the use of '-trailers', note that it
	   is the equivalent of sacrificial goats blood. It won't do
	   anything to solve the problem, but if problem fixes itself then
	   someone can claim deep magical knowledge.

9 Miscellaneous.

	Any other associated stuff that didn't fit in anywhere else gets
	dumped here. It may not be relevant, and it may not be of general
	interest but it is here anyway.

9.01 Bad Vendors

	#define SOAPBOX

	There used to be some horror stories here about dealings with
	Cabletron and Xircom. They were pretty ugly and gruesome.
	Basically these companies are the ethernet equivalent of
	what Diamond is to XFree86. They do not want to release
	vital information on low-level programming of their hardware.
	For something like Linux, where the source code for everything
	is out in the open, this makes their hardware difficult or
	impossible to use. However, like Diamond, when confronted
	with the fact that they are losing sales from Linux/BSD users,
	they basically shrug it off, saying that it is only a small
	percentage of the total sales. If you can afford the time,
	drop these vendors a note (via e-mail or snail-mail) and tell
	them politely that the fact that they don't support open
	software systems such as Linux has forced you to exclude them
	from the vendors that you are purchasing hardware from. It may
	not make any immediate difference, but it might make you feel
	better. Besides, a few seconds of your time is a cheap price
	to pay for *all* that free Linux software you are using. 8-)

	#undef SOAPBOX

9.02 Closing

	If you have found any glaring typos, or outdated info in this
	document, please let one of us know. It's getting big, and it
	is easy to overlook stuff.

	Paul Gortmaker		<[email-masked]>
	Donald J. Becker	<[email-masked]>

		=========== end of Ethernet HOWTO ============