Wayne Stewart wrote:
On Aug 13, 10:59 am, "Michael J. Mahon" <mjma...@aol.com> wrote:The drive parameters were hard-coded into the ROM routines. It's possible that this was done overtly to keep users from upgrading their drives inexpensively, but it was also true that standard methods for reading drive parameters from the drive itself were just beginning to become common (remember how you used to have to tell the BIOS that you had a "type 44" drive, etc.?).Well, the Vulcan 40 ROM seems to work with a 20 and 40mb drive but the Vulcan 20 doesn't work with any 40mb drives. The Vulcan 100 works with smaller drives but not the other way around. Makes me suspicious.
That behavior is also consistent with the release order of the drives/controllers. It is not surprising that newer controllers would work with older drives, and not vice versa.
You are correct that the ROMs were coded for certain drive parrameters. To me it looks like they only chose drives that matched that particular parameters. Makes sense as any 40mb drive they supplied would work with all their 40mb ROMs.
Right. I expect they picked drives that had the same geometries that were hard-coded into the ROM. -michael NadaNet file server for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."