Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!trwind!venice!press
From: press@venice.SEDD.TRW.COM (Barry Press)
Newsgroups: comp.periphs.scsi
Subject: Re: BIG problem with 1542B and Quantum
Message-ID: <1091@venice.SEDD.TRW.COM>
Date: 13 May 91 16:14:42 GMT
References: <262@wyvern.uucp> <283400107@adaptx1>
Reply-To: press@venice.sedd.trw.com (Barry Press)
Organization: TRW Systems Engineering & Development Division, Redondo Beach, CA
Lines: 28

In article <283400107@adaptx1> neese@adaptx1.UUCP writes:
>I do not know about Microport or the Columbia drivers, but I do know what
>is causing the floppy problem.  The drivers have either failed to reprogram
>the bus on and off times or they have incorrectly programmed the bus on and
>off time of the adapter.  By default the adapter uses 11 micro-seconds on and
>4or 5 off.  This is fine in a single threaded environment, but what happens
>in a multi-user environment is:  The floppy DMA will be starved.  The only
>way around this is to program the bus on time to 7 micro-seconds or less.
>The bus off time will be fine at 4 micro-seconds.  This will allow enough
>time for the floppy DMA to be done without starving it.

I'm wondering if this relates to a problem I've seen running FASTBACK under 
DOS.  I have a Northgate 25MHz 486, with a 1542B, Maxtor 200MB drive, and
one each 3.5 and 5.25 floppy.  When I run FASTBACK with the processor on
at full speed, it's lucky to manage a track per minute or so.

If I slow the processor down, then FASTBACK runs mostly normally, but the
transfer rate to the floppy is still less than I've seen on a true blue AT.

Is it possible that the problem you mentioned is affecting this as well?
What are the "right" bus timings under DOS (5) for this machine?  Are there
disk vs. floppy speed trades by making changes?

Thanks.


-- 
Barry Press                                 Internet: press@venice.sedd.trw.com