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From: shannon@sun.uucp (Bill Shannon)
Newsgroups: net.unix-wizards
Subject: Re: 4.2BSD DMF32 DMA driver experience, anyone?
Message-ID: <1317@sun.uucp>
Date: Wed, 27-Jun-84 00:27:21 EDT
Article-I.D.: sun.1317
Posted: Wed Jun 27 00:27:21 1984
Date-Received: Sat, 30-Jun-84 02:26:06 EDT
References: <7554@rochester.UUCP>
Organization: Sun Microsystems, Inc.
Lines: 15

When I wrote the original DMF driver at DEC, I did some crude
measurements with and without DMA on a VAX-11/730.  At that
time, with a prototype DMF-32, my measurements showed that it
was more efficient* to not use DMA.  That's why the DMA code is
commented out in the distributed driver.  (The code used to
work under 4.1 but was probably not modified for 4.2.)  Has
anyone done any measurements recently with real and look-alike
DMF's and other cpu types?

				Bill Shannon
				Sun Microsystems, Inc.


* more efficient == greater number of aggregate characters per second
with less cpu overhead.