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From: jbvb@FTP.COM ("James B. Van Bokkelen")
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: 3C500 slow !! ??
Message-ID: <9105151643.AA11373@ftp.com>
Date: 15 May 91 16:43:42 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: jbvb@ftp.com
Organization: The Internet
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The problem is that the 3C500 is a very old design; it only has one buffer
on board, so you're either transmitting, copying a packet out to the board,
receiving, or copying the packet into the host.  You can't do two at once.
This makes the card very sensitive to hosts that try to send several packets
in close sequence (you miss the 2nd and subsequent packets), or nets where
there is a significant amount of broadcast traffic (a broadcast is likely to
tie the card up and make it miss a packet directed to it).

We recommend that you turn DMA off when using 3C500-family cards in 80286 or
greater processors, so you're doing about as well as you can with our driver.
We recommend configuring the TCP window to 1024, and disabling the "stream"
feature of Interdrive; these may help some.  Presumably Novell tries to
avoid getting overrun as well, but this inevitably slows you down.  If our
direct driver manages to out-perform Clarkson's, it is probably because it
has gotten more tweaking over the years.

In summary, the only thing you're doing wrong is using low-performance cards.
Anything currently on the market will perform a lot better...

James B. VanBokkelen		26 Princess St., Wakefield, MA  01880
FTP Software Inc.		voice: (617) 246-0900  fax: (617) 246-0901