Johnny Billquist wrote:
On 2015-11-27
19:34, Mark J. Blair wrote:
On Nov 26, 2015, at 04:29, Jerome H. Fine
<jhfinedp3k at compsys.to>
wrote:
After that worked successfully, I became disappointed
that I had to deface the floppy media with the extra holes. The
simple solution was to use a DPDT switch and flip the detection
circuits so that the RX03 drive would signal a double-sided media
what there was a single-sided index hole and the DPDT switch was
in the alternate position.
Wouldn't that approach result in the sectors being shifted with
respect to the index hole vs. the case where the conventional index
sensor positions are used? I would imagine that it's a moot point if
the disks are being formatted, written and read on the same drive,
but I can imagine interoperation issues if you later punch the second
jacket window to read/write the disks on an unmodified drive.
If the drive were to use the same offset from the index hole to data,
and so on, yes.
But why would a drive keep those constants the same if the hole moved?
I was also concerned about that afterwards. BUT, without
realizing that it might be a problem, I just tested out the concept
by adding the double-sided index holes (one hole on each side
of the cardboard holding the actual media in the double-sided
hole position).
I then attempted to read and write the first side of the floppy
media which had been LLF, read and written initially using the
single-sided index holes. It all worked.
I then attempted to read and write the first side of the floppy
media which had been LLF, read and written initially using the
double-sided index holes. Again, it all worked.
So I don't know exactly how the hardware timing worked when
the index hole was shifted, but in the case of the DSD 880/30,
it did not cause a problem. The media could be LLF using either
index hole and then read and written using the other index hole.
Of course, once I installed the DPDT switch, there never needed
to be two pairs of index holes. That might have been the answer
in some cases. The net result was that I never had a problem.
Jerome Fine