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Date:      Fri, 17 Jul 1998 08:54:14 -0400 (EDT)
From:      Bill Paul <wpaul@skynet.ctr.columbia.edu>
To:        hackers@FreeBSD.ORG
Subject:   Obtaining 3Com programming documentation
Message-ID:  <199807171254.IAA06263@skynet.ctr.columbia.edu>

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Anybody know the right place/person from which to obtain programming
documentation for 3Com ethernet chips? We recently received two Dell
GX1 systems as donations from Intel as part of a testbed system that
some people in the EE department will be using in cooperation with a
researcher from Intel. The systems actually have the Dell markings
replaced with big 'Donated by Intel' signs but you can still tell they're
Dells.

Anyway, the machines have integrated 3Com 3c905B 'Cyclone' chips in
them which, of course, don't work right in FreeBSD. My experiments so
far indicate that the problem is that the first time a packet is received,
the chip generates an interrupt flood. After the interrupt routine is
invoked, there's a function that's supposed to remove the received frame
from the chip: this function is supposed to read a status register from
the window 1 register set so that it can learn the size of the packet,
but the value read is always 0. This means the packet is never taken
off the chip and the chip keeps interrupting forever, which wedges the
system pretty tightly.

I have the source for a Linux driver which claims to support this chip,
but an actual programming manual would be better. Of course, 3Com doesn't
seem to have any such info on their web servers. Any other driver 
programmers know the right trees to shake at 3Com? I really need to get
this stupid thing working to make the Intel guy happy (to say nothing
of certain Columbia EE faculty).

-Bill

PS: These systems also came with Adaptec 2940 U/UW controllers with
the 7895 chip. This forced me to download the CAM snapshot in order
to even get the machines running. The CAM stuff seems to work fine
so far, though at the moment we only have the one SCSI disk attached.
Please tell me there will be driver support for these bastiches in
FreeBSD 3.0-RELEASE.

PPS: Amusingly, whoever assembled the systems at Dell used the wrong
pre-loaded LoseNT 4.0 disk image which did not have the correct driver
loaded to support this controller: the machines blue-screened immediately
after we first turned the systems on, with the Intel researcher looking
on. I got a good laugh. Well, for a little while. Then I had to re-load
LoseNT.

PPPS: This is the second time I've had to do FreeBSD development work as
part of my job. (The first time was writing the ThunderLAN driver.) Maybe
the world isn't so screwed up after all.

-- 
=============================================================================
-Bill Paul            (212) 854-6020 | System Manager, Master of Unix-Fu
Work:         wpaul@ctr.columbia.edu | Center for Telecommunications Research
Home:  wpaul@skynet.ctr.columbia.edu | Columbia University, New York City
=============================================================================
 "It is not I who am crazy; it is I who am mad!" - Ren Hoek, "Space Madness"
=============================================================================

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