15 May
2007
15 May
'07
6:39 p.m.
On Tue, 15 May 2007, Chuck Guzis wrote:
I hadn't realized that there was a norm for CP/M
floppies. You know,
the "recommended" 512-byte sector "packing" in the uPD765 literature
is 8 sectors--and indeed, early PC-DOS used just that.
I once asked Gary Kildall, "What is the standard format for 5.25" disks
with double density?"
He replied, " 8" single density."
If the first sector on the track is consistently
missing (not always
the lowest-numbered; some systems skew the tracks for better
performance), you might be able to recover it by slowing the drive a
bit to allow the first sector IDAM to move outside of the 765 "blind
spot" at the beginning of a track (although the 765 formats a track
with an IAM at the start, it never reads it).
For that same problem, I prefer "masking off" the index pulse. As was
discussed earlier, that can be done in almost any way that permits
interrupting that signal in the cable, or, with MOST drives (but NOT
Teac!), by covering the index hole of the disk jacket.
--
Grumpy Ol' Fred cisin at xenosoft.com