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From: aland@infmx.informix.com (Colonel Panic)
Newsgroups: comp.sys.att,comp.unix.sysv386
Subject: Dirty Rotten DMA problem (?)  Simultaneous tape & diskette use
Keywords: DMA
Message-ID: <1990Oct31.190027.8613@informix.com>
Date: 31 Oct 90 19:00:27 GMT
Sender: news@informix.com (Usenet News)
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Organization: INFORMIX Professional Services ("Peace thru Normalization")
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Originator: aland@cougar

I just encountered some strange i/o errors, and I'm looking for some
collective wisdom...

Platform: AT&T 6386E/33, 24MB of memory, standard AT&T/Wangtek 125 MB
          streaming tape, SV/386 Rel 3.2.2

Situation: while doing a mass cpio to the streaming tape, I try to
           format some 3.5" floppies or dd some disk-resident floppy
           images to them.  I keep getting i/o errors on the diskettes.
           If I try the same operations while the tape drive is not in
           use, no problems arise.

Since both are using DMA, I suspect that the DMA buffering in the
kernel is going haywire.  Current pertinent kernel parms are DMAEXCL=0
(allow simultaneous DMA) and DMAABLEBUF=256.

Does anybody have any other ideas as to possible other causes and/or
possible solutions?

thanks in advance.

--
Alan Denney      aland@informix.com      {pyramid|uunet}!infmx!aland

I'm Pro-Anarchy...   and I Vote!