Chuck Guzis wrote:
On 01/23/2013
07:50 PM, Dave Land wrote:
Well, that blows that idea. I don't HAVE any
SSSD disks, just DSDD.
Back to the drawing board I guess.
Most 8" disks (assuming that the aperture in the jacket is in a
position that matches the index sensor on your drive) will work just
fine in either density or side-edness. There is no difference in the
media coating.
First, I confirm that every 8" media I every encountered
was able to be both SD and DD as well as SS and DS
as far as the media coating was concerned (except for media
purchased from one company which had a high failure rate
when used a DS), The index hole is another matter.
My experience with the DEC RX02 floppy drive and the
DSD 880/30 drive may be helpful. The DSD 880/30 drive
emulates 3 * RL02 (NON-removable for this hardware)
and a single RX03 floppy drive which can accept any
8" standard floppy media which the DEC RX02 accepts.
About a dozen companies sold these media, with both
unformatted and formatted being available. The DEC RX02
drive is NOT able to perform a Low Level Format from
scratch, but if the 8" floppy media has already been LLF
and is relatively undamaged, then the DEC RX02 is able
to toggle between SSSD and SSDD usage. On the other
hand, the DSD 880/30 is able to do an LLF from scratch
either as SS or DS, depending on the index hole.
At one point I specifically purchased DSDD media to be
used with this drive, but was not able to find them consistently
when additional media were needed. The DSD 880/30 has
two detection circuits which allow it to use two different index
holes. When SS media are used, the index hole is expected to
be about 3 mm above the centre hub hole and about 1 mm offset
to the right. (The bottom of the floppy media is the edge which
enters the floppy drive first and the top surface is the surface
the suppliers label.) When DS media are used, the index hole
is expected to be about 3 mm above the centre hub hole, but
this time offset to the right about 10 mm.
My first solution was to punch an extra pair of holes in the jackets
and cover up the SS index hole when I wanted to use SS media
as DS media. Later, I managed to add a DPDT switch into the
detection circuits and "encourage" the DSD 880/30 drive to
believe that a SS index hole was actually the DS index hole
by reversing the circuits using the switch. In the other position,
the switch changed the circuits back to the original function and
the SS media reverted back to being SS again with the DS media
also being detected correctly.
Why every 8" floppy media were coated identically on both sides
I don't know, but that was the standard with every SS 8" floppy
soft sectored media I have ever seen. EXCEPT that when I
encountered a few 8" floppy media with a DEC label, the failure
rate as SS media was normal. HOWEVER, when the DSD 880/30
drive attempted to do an LLF, about 10% (if I remember correctly -
this was 25 years ago after all) failed the DS attempt at an LLF.
How DEC managed to obtain media which were degraded on the
second side so frequently when none of the other 8" floppy media
I encountered had that problem (i.e. the other media were able to
either LLF both sides or none and VERY few failed the DS LLF)
I can't explain, but that was my experience.
Jerome Fine
