NetNews Usenet Archive 1992 #26/NN_1992_26.iso/spool/comp/os/msdos/programm/10493

Internet Message Format | 1992-11-10 | 1.7 KB

Path: sparky!uunet!munnari.oz.au!metro!usage!csdvax.csd.unsw.edu.au!86b0062
From: [e-mail] (Sam Lander)
Newsgroups: comp.os.msdos.programmer
Subject: Max DMA rate from 386 to D/AC's
Message-ID: <[e-mail]>
Date: 11 Nov 92 13:45:41 +1000
Organization: University of New South Wales
Lines: 27

I want to send data out to 4 12 bit D/ACs as fast as possible. (There is
more than that in this story, but for now, that is enough.)

At the moment, I am sending data byte by byte using I/O instructions
to a PC bus D/AC card. I have to perform 9 byte output instructions to get the
data from memory onto the card's analogue output lines. A transfer cycle
takes about 18 usec to complete. This is about 55kHz or 55kx9 = 495kbytes/sec.

My machine is a 33Mhz 386 AT bus box, without too much that looks special to
my (untrained) eye. I have no idea at all about wait states etc.

I am looking at building a new D/AC card using the AT bus that will be driven
by my the 386's DMA controller chip. I am looking for data transfer rates in
the order of 1Mbyte/sec or better. the CPU will be doing nothing special
and so I am happy for its performance to be reduced by up to 90%. The
key factor is getting the data out as fast as possible on this machine.

Could someone give me an idea of the data transfer rates I might expect from
such a setup?  Failing that, what is a good reference on this topic that
might tell me?

Sam Lander

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Sam Lander, Department of Psychology, University of New South Wales, Australia.
[e-mail] or [e-mail]. ... Phone [phone].