4 Mar
2023
4 Mar
'23
11:46 a.m.
On Thu, Feb 23, 2023, 08:44 Will Cooke via cctalk <cctalk(a)classiccmp.org>
wrote:
That was done because the controller manufacturer didn't make the drives. A
system integrator or even the end user was expected to use the controller
with some arbitrarily selected drive.
The Apple Profile was an entire preconfigured subsystem in a box. Apple
bought the drive mechanism (only, no electronics, not even the normal drive
electronics), built the controller, packaged it, and nothing was
user-upgradeable. It wasn't even considered dealer-upgradeable. The
controller and drive mechanism were permanently associated. If the drive
mechanism failed, service replaced it with an identical mechanism.
The Profile controller could deal with drives with a varying number of
cylinders, hence the existence of both 5MB and 10MB models, but was not
designed to support more heads like a general-purpose SASI bridge.
On 02/21/2023 10:48 PM CST Eric Smith via cctalk
<cctalk(a)classiccmp.org>
wrote:
Profile trivia:
The firmware _inside_ the Profile is strange in that it doesn't actually
KNOW the size of the Profile it's installed into. At power up, when the
drive reads the home block, the drive size is stored there. That's done
when the drive is formatted. There is different formatter firmware for
5MB
and 10MB drives.
I think that was rather common with early SASI/SCSI controller boards that
were separate from the drive.