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From: j@uriah.sax.de (J Wunsch)
Newsgroups: comp.os.386bsd.bugs
Subject: Re: FreeBSD, fd0d: hard error
Date: 25 Sep 1994 22:03:34 +0100
Organization: Private U**X site; member IN e.V.
Lines: 23
Message-ID: <364oj6INNka5@bonnie.sax.de>
References: <33j9hp$41l@sol.sun.csd.unb.ca> <34a91e$h2f@sol.sun.csd.unb.ca> <34iv96$ik4@pdq.coe.montana.edu> <34lk6g$d44@orion.cc.andrews.edu> <CwCMrD.4p8@sneaky.lonestar.org>
NNTP-Posting-Host: bonnie.sax.de
gordon@sneaky.lonestar.org (Gordon Burditt) writes:
>Adaptec's EZ-SCSI manuals note that the default bus-on and bus-off
>times on the AHA1542-whatever are long enough to interfere with
>floppy or floppy-tape I/O due to DMA starvation. I'd expect
>that the error codes would reflect DMA underrun (writes) or
>overrun (reads), which I'm not seeing in the posts, but maybe
>there is a problem with error reporting or retry logic.
Error reportings should be as accurate as the underlying FDC is.
As far as i remember, *BSD does not use the default Adaptec DMA bus
timings. Anyway, there's still an interference between heavy SCSI
activity and the floppy. Hence the DMA overruns (the FDC has only an
overrun flag, which is also reported on underruns) are caught inside
the driver and silently retried. This is not one of the latest
changes, it did already exist in FreeBSD 1.1.
--
cheers, J"org work: joerg_wunsch@tcd-dresden.de
private: joerg_wunsch@uriah.sax.de
Steinbach's Guideline for Systems Programming:
Never test for an error condition you don't know how to handle.