Substituting DSHD for DSDD disks (or DS2D if you prefer)

Chuck Guzis cclist at
Mon Oct 26 02:52:50 CDT 2015

On 10/25/2015 11:12 PM, tony duell wrote:

> Not always! The original Sony full-height drives (the 600rm ones)
> have a disk-inserted sensor positioned exactly where that hole is. So
> if you insert an HD disk the drive doesn't detect it. It is rumoured
> this was deliberate (positioning of the HD hole) so that you couldn't
> use the wrong disks and have reliability problems.

Yes, the Sony OA-D32 drives.  Single-sided 600 RPM.  One *could* argue, 
that, given the data rate, it's already "high density" (of a sort).  I 
worked out a BIOS for a Z80 CP/M system called a Preis around 1982, when 
the drive was pretty new.  It was a luggable and had a hard disk option 
as well.  I don't know whatever became of them--but I still have the 
BIOS listing in my files.

I don't think that anyone had any thoughts about putting such a drive in 
with a controller that would do 1Mbps.  Sony never alluded to it in 
their documentation.

The battle of the "pocket floppies", IIRC, hadn't yet been settled in 
1982.  We could just as well have wound up with the Shugart/Dysan 3.25" 
floppy--or worse, the Hitachi 3" disks as used in the Amstrad machines.

I've still got a couple of 3.5" ED drives, along with blank media--there 
was a trend that didn't last long...


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