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From: clements@bbn.com (Bob Clements)
Newsgroups: comp.protocols.nfs,comp.dcom.lans,comp.protocols.tcp-ip.ibmpc
Subject: Ethernet cards, PC/NFS, DS8390
Message-ID: <46100@bbn.COM>
Date: 26 Sep 89 18:47:17 GMT
Sender: news@bbn.COM
Followup-To: comp.dcom.lans
Lines: 52

I've just wasted a fair amount of time chasing a problem.  I'll briefly
summarize it, to try to save others the time and pain, and then ask
a question.

On an IBM-PC using PC-NFS, I have been getting a steady low level
of obscure errors from the Microsoft Linker, and occasionally an
error from the C compiler, caused by non-repeatable data errors.
They recently became more frequent and I decided to track them
down to see whether I had a sick PC or network or a conflicting
TSR or what.

I switched PC mainframes from a 386 to a 286.  Problem still
there.  Reinstalled PC-NFS.  Still bad.  Used COPY and DIFF to
capture some bad data and then examined it.  Observed a pattern
of 15 or 16 bytes being copied over another group of 15 or 16
bytes at a location 64 bytes later in the file. (If you've been
there before, this probably tells you the answer.  It didn't tell
me, yet.) I swapped ethernet cards.  The problem went away.  (I
hadn't swapped them before because I didn't want to bother
updating the ethers files.)

Analysis:

    PC-NFS (like all sun NFSs) is implemented over UDP, but with
    UDP checksumming turned off.  (^%$&@^#!$% !!!)

    If an ethernet packet gets clobbered, the error may therefore
    not be detected by NFS, since it isn't checksumming.

    I can't find my reference, but I believe I've heard that this
    particular failure mode is one present in early revs of the
    DS8390 ethernet chip. (I sure hope my memory is right;  if
    not, I'm unfairly maligning National. They did have a number
    of glitches and I THINK this is one of them.)

    We have been having some broadcast storms lately, increasing
    the odds of this failure and causing the recent increase in
    symptoms.

    The new card has a newer rev DS8390 (8824 versus 8742C4 date code).

I should have recognized the failure mode earlier.  I wrote the
WD8003E and 3C503 drivers in the Clarkson collection (though they're
not what I was using with PC-NFS, of course) so I should have known.

My questions (which I should get purchasing to check, but as long
as I have the floor): 1) Anyone know where I can get a new
date code DS8390 in quantity one?   2) Any idea if Western Digital
will upgrade this WD8003E after it's out of warranty? (It's not
their fault, of course.)

Bob Clements, K1BC, clements@bbn.com