3 Oct
2007
3 Oct
'07
10:31 a.m.
Tony Duell wrote:
IIRC, the early Apple disk drives used a 13 sector
format. Apple worked
out a modification (basically allowing some bit patterns that were
illegal before) to pack 16 sectors on to each track. The modifications to
a real Apple cotnroller were 2 new PROMs, one was the state machine logic
(the modified state machine could physiaclly read both 13 and 16 sector
disks), the other was the bootstrap firmware, and IIRC the new firmware
would only boot 16 sector disks. Of course an unmodified controller could
only boot (heck, could only read) 13 sector disks.
Aha, OK - that's plausible I suppose... *reading* either format is OK, but
booting isn't... releasing an upgrade which could no longer make any sense of
the old format would seem a funny thing to do :-)
Anyway - progress of a sort. I've got hold of a proper Apple Disk ][ drive,
and some 3.3 media - and the clone machine boots that quite happily. The 3.3
media I have *won't* boot in the half-height ALPS drive I had, suggesting that
there's a fault with the drive (heads cleaned with IPA just for the record,
there's evidently something else up with it).
I haven't tried the 3.2 media with the Disk ][ drive yet, but if you're right
about the above then it won't boot (although if catalog works with both disk
formats then I should be able to boot via 3.3 and catalog the 3.2 disk).
Aha... IIRC, 3.2 is 13 sector, 3.3 is 16 sector. If
your clone is
expecting 16 sector disks, it will not boot 3.2 AFAIK.
Yes, that seems to be the concise answer :)
Still, I'm happy because I've seen it boot *something* - major plus point
considering that the machine's a clone rather than the real thing (and useful
to know that the disk interface hardware's functional).
cheers
Jules