21 Nov
2005
21 Nov
'05
7:20 p.m.
BTW, if someone out there has the HP150 Technical
Reference manual
set, and it says something about what the expected on-disk format is,
I'd like to know more about that. Similarly for anyone who has some
idea what the 9121/9122 drives think about where they're allowed to
scribble on the disk.
I do have the HP150 technical reference manual and the 150-II update, but
from what I rmemeber it says remarkably little about
the physical disk
format. I wrote linus programs to read the 9114 disks and there
was
nothing of use in said manual.
From what I recall, the single and double sided formats
are
somewhat different, though.
There is also the issue of the bad track replacement. HP reserved a few
tracks at the end of the disk, and put something on the innermost track
(79) to indicate that ome of the user tracks was bad and should be
replaced by one of the reserved ones. Oh, they also wrote the media usage
count there (that's what causes the drive LED to flash when the disk is,
in HP's opinion, too old). All this was handled by the _drive_ unit, not
by the 150, and I've never seen it documented anywhrre. Alas I just had
to igore it and assume I was using good enough disks that no tracks were
replaced (this has worked -- so far).
-tony