27 Nov
1999
27 Nov
'99
12:28 p.m.
It would be interesting to see SOMETHING for the 33C93, but what puzzles me
more than anything else is the question of how to cook up a quick and dirty
translation from the CP/M drive/track/sector specification to a logical
block structure as is used on SCSI/SASI devices. CP/M 2.2 is so much nicer
if you have a maximal TPA which won't happen if one's using table lookups
and stuff in place of computations to determine which block contains what
the OS is in sector ss of track tt on drive x. You see, if this is
implemented on a bridge controller which talks SCSI to the system, but whose
drives are ST-506 interfaced, there are good ways and bad ways to allocate
blocks. It's simple enough to do one layer, but if you have to deal with
two, how you do one will have substantial impact on how the other works out.
Dick
-----Original Message-----
From: Ethan Dicks <ethan_dicks(a)yahoo.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, November 27, 1999 3:43 PM
Subject: Re: CP/M-80 drivers for WD33C93 ???
--- Allison J Parent <allisonp(a)world.std.com> wrote:
owing
I've heard the 33C93 is a really buggy chip.
Early versions have their (well documented) problems. Commodode elected to
use the WD33C93 with the autobooting SCSI cards - A2091 and up including
the A500 slap-on A590 (either SCSI _or_ XT-IDE drives would work on it to Commodore's custom controller chip between the
Amiga and the 33C93) and
on the motherboard of the Amiga 3000.
The wisdom in the Amiga arena is that even though C= shipped rev 02 and
rev 04 chips, you need the last version ever produced (rev 08?) to take
advantage of proper disconnect/reconnect operations and to have a full
7-device chain. The older chips work OK if you have one or two disk
devices, but have problems with four or five disks, a CD-ROM and a tape
drive.
There is example code for the WD33C93, not for CP/M, but for (Net|Free)BSD
on the Amiga.
Also, if anyone is looking for a few rev 02 chips, I have a tube of them
that I'm keeping as Amiga spares. I could let a couple go, depending on
how much over shipping I'm offered.
-ethan
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