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From: ephraim@wang.UUCP (pri=8 Ephraim Vishniac x76659 ms1459)
Newsgroups: net.micro.mac
Subject: About Apple's Sample SCSI driver
Message-ID: <847@wang.UUCP>
Date: Mon, 28-Jul-86 09:38:29 EDT
Article-I.D.: wang.847
Posted: Mon Jul 28 09:38:29 1986
Date-Received: Wed, 30-Jul-86 00:57:18 EDT
Distribution: net
Organization: Wang Labs, Lowell MA
Lines: 27

After receiving the new Software Supplement on Friday, the first thing
I did (besides open the envelope) was to try out the sample SCSI disk
driver.  Porting to MDS was no problem.  Getting the drive running was
no problem.  Getting the drive to boot was a problem.

The solution (for a Rodime 652 drive) was to change the "reliable" use
of _SCSIRead to an "unreliable" use of _SCSIRBlind!  With the normal
reads, the drive always hung at boot time, with the access light on.
With blind reads, no problem.

Other tweaks:

In DiskPrime, the bounds checking incorrectly prevents you
from reading the last sector of a partition.  Change "bge" to "bgt".  I
can only conclude that neither the developer nor any beta tester tried to
scan their entire drive, otherwise this bug would have been spotted long
ago.

In RealInstall, you can free up some system heap space by adding a call
to _SetPtrSi~%to trash the area held by the installation code.  The size
to change it to is simply RealInstall-Disk.

If there's interest, I'll post source for my SCSI installer (MDS assembler)
to net.sources.mac.  To demonstrate interest, send mail to me:

Ephraim Vishniac
decvax!wanginst!wang!ephraim