On Thu, Feb 23, 2023, 08:44 Will Cooke via cctalk <cctalk@classiccmp.org> wrote:
> > > > On 02/21/2023 10:48 PM CST Eric Smith via cctalk <cctalk@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. > 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.
