Re: Unidisk vs. Disk II

[shoppa@altair.krl.caltech.edu (Tim Shoppa)]

In article <4fidah$1cq@urvile.msus.edu>,
Bill Scheffler <schefflr@news.msus.edu> wrote:
>Dave Althoff (dalloff@freenet.columbus.oh.us) wrote:
>: ierickson@ewu.edu wrote:
>
>: There seems to be a common problem with pairs of Disk ]['s, in that after
>: a while, Drive 1 will refuse to boot.  So, you swap the drives so that the
>: Drive Formerly Known As #2 will boot just fine, and the old Drive 1 will
>: still read and write just fine.  This is an odd situation, but it explains
>: why so many boot-drive Disk ]['s are marked "Drive 2".  In my parents'
>: case, the problem recurred.  I switched the disks back (so the
>: formerly-non-booting Drive 1 was once again Drive 1) and the system worked
>: just fine.  Disk ]['s are funny that way.
>
>	Boy, I thought I was the only one with that problem.  Anyone want 
>to give a technical reasons why this is...aside from ware and tear?

The boot code (from $C600 to $C6FF on the Disk II controller card)
is pretty stripped down, and not nearly as intelligent as the full-blown
RWTS routine that gets loaded when DOS is read in.  In particular,
there's probably a lot of error recovery/retry code missing from the
boot ROM's routine.

Tim. (shoppa@altair.krl.caltech.edu)