[Coco] Diskettes

[Willard Goosey]

On Mon, Jun 27, 2011 at 09:30:12PM -0500, Steve Ostrom wrote:
> I found a set of eight diskettes that I have never seen before.  They 
> are 3M DEC RX 50 disks.  A Google search says the DEC RX 50 drives were 
> very unusual, with DEC trying to cram a lot of data on one diskette 
> using odd parameters.  

The RX50 drive is very weird.  It's quad density, 80-track, but I don't
quite know rather to describe it as single-sided or double-sided....

It looks like 2 half-height drives in one full-height package but it's a
single drive, sharing (IIRC one drive motor and one head-moving servo?
that runs both "drives") 

>From what I understand, it *pretends* to be a 720K double-sided drive,
by combining 2 qd single-sided disks!  Disks were usually used in pairs,
one as "side 1" and one as "side 2".  The user had to be careful to put
the correct disks in the correct slots.

I've got one, salvaged out of a Rainbow or a Pro-350.  I tested it on my
CoCo but without proper 80-track floppies it didn't work so well.

>Has anyone ever tried to use one of these 
> drives?  These diskettes did not read in my Coco drive and I decided 
> not to try to reformat them for use.  There might be data on the disks 
> that would be interesting to someone, or they might be blank.

Well, I know formatting HD 5.25" disks as DD doesn't work, but I've
never tried it with quad-density disks.  

Gods only know what those disks might have on them.  The Rainbow was a
CP/M and MS-DOS machine, the Pro-3x0 line were PDP-11's, I've seen
regular PDPs with an RX50, and I think I once read that some VAXen want
to load CPU microcode off an RX50 on power-up.  I'm not sure where the
old-school DECheads hang out on the Net, but they'd probably be glad to
see those disks.

Willard
-- 
Willard Goosey  goosey at sdc.org
Socorro, New Mexico, USA
I search my heart and find Cimmeria, land of Darkness and the Night.
  -- R.E. Howard