Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!Philip
From: Philip Prindeville@UDEL.EDU, philipp@larry.mcrcim.mcgill.EDU
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re:  Western Digital board
Message-ID: <8805110207.AA04794@Larry.McRCIM.McGill.EDU>
Date: 11 May 88 02:07:12 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 11

Well, my experience on some of the memory mapped boards has been that
it is indeed efficient.  One of the very high performance serial boards
(1.5mbps) that I am working with has 512K of memory, of which the top
256k is reachable (as 4x16kb windows).  In the CMU PC/IP I keep the
packet buffers there, and never have to do any copying.  It is _very_
fast (almost 90% line utilization).  I was working with a few ARCNET
boards some months ago, and they were also memory mapped.  It does make
for faster copies (if they are 2 wait states or less) than DMA.  Problem
was that they could only hold 4 packets, so you had to build your packets
and then copy them.  Sigh.

-Philip