15 May
2007
15 May
'07
6:26 p.m.
It's entirely possible that the drive used to
create the diskettes
was somewhat out of alignment. You may have to "unalign" a drive to
successfully read these. This is more common than you might think.
Btw the Align/Test function of ImageDisk is very useful for this - it
you can seek to a cylinder and get an audible beep which increases
with the number of sectors IDs found match the cylinder - very handy
when you need to align a drive to a disk (which I've had to do a number
of times).
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).
I've had to do this for a number of systems, Cromemco being the most
notable ... I find slowing the drive by about 10rpm makes a huge
difference on some disks (One of the reasons I like TEAC drives -
very easy to set the speed).
And yes - 10x512 is quite common, and can be accomodated with a
765.
Regards,
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html