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

Mon Oct 26 03:04:06 CDT 2015

and the  first  hp-150 drive set,   the  hp-9121, was single sided double 
density SS/DD discs (270Kb).  
sure was glad  when the  9122 came  out!
Always looking for more HP-150  stuff for our  display... any one have a 
monarch butterfly advertising poster?
Ed# _www.smecc.org_ (  
In a message dated 10/26/2015 12:52:56 A.M. US Mountain Standard Tim,  
cclist at writes:
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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