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From: neese@adaptx1.UUCP
Newsgroups: comp.periphs.scsi
Subject: Re: <12788@xstor.com>
Message-ID: <283400137@adaptx1>
Date: 11 Jun 91 02:37:43 GMT
References: <12788@xstor.com>
Lines: 32
Nf-ID: #R:xstor.com:12788:adaptx1:283400137:000:1306
Nf-From: adaptx1.UUCP!neese    Jun 10 10:51:00 1991


>>>SCSI is easier to integrate and (with some drivers) more reliable.
>
>> I've had complaints from Windows and Desqview over DMA-intensive
>> devices like my scanner and DMA-heavy activities like Fastback
>> (backup software).   Will this be a problem with bus-mastering
>> SCSI devices?
>
>The only DMA problem I've heard of with the Adaptec board has to do with
>operating the floppy and the transfering from/to the scsi-bus at the time;
>if the bus on/off time is not set properly, the floppy will starve for data.
>
>[Roy, if you're listening, chime in - I know you know the realy story, 'cuz
> you're the one who told me about it!]
>STUFF DELETED<

Tim's right.  The default bus on time for the 154x is 11 microseconds.  This
is long enough to cause a floppy data underrun condition when overlapped
disk I/O is performed with floppy I/O.  The bus on time needs to be set
to 7 microseconds to cure this.
I wrote SETSCSI just for this purpose.  I put it in a batch file before
calling FASTBACK and then call SETSCSI with no arguments afterwards to reset
the 1542 back to defaults.  Cures the problem like so:

setscsi -n:7
fastback (or your favorite program)
setscsi

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