flash (or ide) storage for unibus 11?

[Jerome H. Fine]

 >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