Re: Linksys card

From: Donald Becker (becker@scyld.com)
Date: Sun Jul 08 2001 - 10:02:31 EST


On Sat, 7 Jul 2001, Ron Alford wrote:

> On Fri, 6 Jul 2001, Jim Roland wrote:
> > Check out http://www.scyld.com/network/ this will contain Donald Becker's
> > current drivers for NICs under Linux (found via google). Any references in
> > search engines to downloading NIC drivers from NASA will either be broken or
> > old. Mr. Becker doesn't work fulltime for NASA anymore, but is still one of
> > those NASA geeks that all of us wish we could have been. :)
>
> Yes, thanks. I had already looked at those pages though. The new NatSemi
> chipsets don't seem to be fully up and running yet.
> You can find Becker's page for this driver at
> http://www.scyld.com/network/ethercard.html

The ns820.c driver works at 10/100, but the 5/18/2001 version still has
two issues:
   automatically switching to 1000 speed with some transceivers
   detecting using 32 bit mode when the 821 is on a 64 bit bus

The second is an interesting point. It appears that the 83820 (64 bit
PCI) and 83821 (32 bit PCI) chips are really exactly the same, including
the PCI ID and pin-out. It appears that the EEPROM is supposed to be
programmed to set a 32 or 64 bit data path, depending on the chip+board.
The design example has the EEPROM set to 64 bits. You can guess the
result: board vendors copy the design example verbatim, and 32 bit
boards ship with the 64 bit setting. Plugging a 32 bit board into a 32
bit slot works, a 64 bit slot results in half the bytes missing. If you
are a board vendor, this is trivially fixed with a hacked driver. But the
sleazy driver fix loses performance for a 64 bit card.

Donald Becker becker@scyld.com
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Second Generation Beowulf Clusters
Annapolis MD 21403 410-990-9993

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