Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!convex!mic!letni!rwsys!merch!cpe!adaptex!adaptx1!neese
From: neese@adaptx1.UUCP
Newsgroups: comp.periphs.scsi
Subject: Re: BIG problem with 1542B and Quantum
Message-ID: <283400112@adaptx1>
Date: 16 May 91 03:46:43 GMT
References: <262@wyvern.uucp>
Lines: 35
Nf-ID: #R:wyvern.uucp:262:adaptx1:283400112:000:1850
Nf-From: adaptx1.UUCP!neese    May 15 11:25:00 1991


>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?

FASTBACK is definately effected by this.  That is why I wrote SETSCSI.  It
allows you to reprogram the above parameters under DOS, so you can get the
full speed of programs such as FASTBACK.
I have usually made a batch file that puts SETSCSI infront of FASTBACK
and then calls SETSCSI again after FASTBACK to restore the values.


			Roy Neese
			Adaptec Senior SCSI Applications Engineer
			UUCP @  neese@adaptex
				uunet!cs.utexas.edu!utacfd!merch!adaptex!neese