On Thu, 27 Jun 2002, Tony Duell wrote:
> > But, ...
> > TEAC drives (and probably some others) wouldn't work with the technique,
> > since they look for drive up to speed by monitoring the index pulse.
> Why did this only affect DISKCOPY? Surely such a modified disk (no index
> pulse) would cause problems with Teac drivs no matter what program you
> were using to read it.
You're absolutely right, of course.
DISKCOPY was merely an example, since the premise of the bet was making a
disk that DISKCOPY could make a working copy of, but that the option board
could not. And, as you said, a no index diskette will cause the Teac
drives to choke on any type of read attempt.
The point was that the OEM 5150 drives (Tandon TM100-2), could read and
write without index. Therefore, since the option board software needed
index, it was possible to create a disk that could be accessed without the
option board, but not with it. Presence of the option board did not
interfere with the "normal" disk I/O.
We used to have to block the index for reading and writing some disk
formats on the PC. For example, some TRS-80 formats, and even some Kaypro
formats, start their first sector too close to the index for comfortable
reading with a 765. We were able to do them, by just putting a piece of
opaque tape over the index hole. But with Teac drives (55B), blocking the
index kept the drive from functioning. For those, we would just interrupt
that wire in the cable, so that the index was seen by the drive, but not
by the FDC.
--
Fred Cisin cisin_at_xenosoft.com
XenoSoft http://www.xenosoft.com
PO Box 1236 (510) 558-9366
Berkeley, CA 94701-1236
Received on Thu Jun 27 2002 - 16:47:39 BST