Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!uunet!fernwood!asylum!romkey
From: romkey@asylum.SF.CA.US (John Romkey)
Newsgroups: comp.protocols.nfs
Subject: Re: IO Errors with Sun PC-NFS
Keywords: PC-NFS
Message-ID: <5602@asylum.SF.CA.US>
Date: 28 Sep 89 06:42:44 GMT
References: <309@massey.ac.nz> <2701@com50.C2S.MN.ORG>
Reply-To: romkey@asylum.UUCP (John Romkey,The Asylum)
Organization: The Asylum; Belmont, CA
Lines: 47

In article <2701@com50.C2S.MN.ORG> craig@com2serv.c2s.mn.org (Craig S. Wilson) writes:
>I use the 3Com 3C501 cards,
>which have no on board intelligence.  I have found that even when I am
>the only user on the network, I get a number of delays.  In fact, it
>seems to be worse, when there are fewer users.  I figure that my pc
>can't keep up with the message rate and throws some messages away.
>
>Am I close?  I can't say that I have investigated this phenomenon too
>closely.  If I had an ethernet controller with onboard intelligence,
>would I have the same problems?

Sort of. The problem is necessarily one of intelligent vs. dumb cards,
though. The problem is that the 3C501 is probably the worst performing
ethernet card on the market. The 3C501 is basically a 3C500 on a
smaller card, with fewer components. No architectural changes. The
3C500 was the first ethernet card available for the IBM PC. It had a
lot of bugs (not surprising) and a major problem with the way
buffering is done - it has only one packet buffer, shared for transmit
and receive. Because of this, you can't receive packets in rapid
succession (never mind back to back) and you can't receive packets
while you're loading the buffer with a packet to transmit. So,
performance is pretty bad.

My experience with intelligent ethernet cards is the only reason you'd
want to run most of them under DOS is to save memory (get the TCP
stack out of DOS memory). Often the programming interface is so
cumbersome that there's more overhead talking to the card than there
is doing the TCP protocol. The best performing smart card I've seen is
the CMC ethernet card, and it does outperform the card I recommend
below, but it's also more expensive. I must admit to not having done
any kind of comprehensive tests among various smart cards, so I can't
give you exact numbers.

For a while, there was an argument that you could use a smart card
with a faster processor in it than your PC and thereby gain in
performance. Recently they've been lagging way behind in this area,
though, and frankly, I'd much rather run my TCP on my 16MHz 80386 than
on an 8MHz 80286 or even slower chip.

I'd instead recommend a different dumb card, like the Western Digital
WD8003E, which is one of the best performing 8 bit ethernet cards, and
also one of the cheapest.
-- 
			- john romkey
USENET/UUCP: romkey@asylum.sf.ca.us	Internet: romkey@ftp.com
"Live the life you love, Use a god you trust,
 and don't take it all too seriously." - Love & Rockets