Cromemco & Persci drives (was PS/2 interface &c)

Roy J. Tellason rtellason at
Tue Sep 18 21:56:31 CDT 2007

On Monday 17 September 2007 23:54, M H Stein wrote:
> -----------------Original Message:
> Date: Mon, 17 Sep 2007 19:50:25 -0400
> From: "Roy J. Tellason" <rtellason at>
> Subject: Re: PS/2 Interface (was: Wang 300 Calc]
> On Monday 17 September 2007 18:57, Tony Duell wrote:
> <snip>
> > I have an S100 amchine called a CASU Super C. It contains a Cromemco CPU
> > board, some other stnadard 64K RAM bvoard, a Micromation Doubler disk
> > controller and CASU-designed boot ROM and seiral interface boards.
> >
> > The disk drive (a Persci) is in a separate box. The 50 wire interface
> > cable is split down the middle adn connected to a pair of DB25s...
> I have a Cromemco "System 3" (?).  It also has a Persci drive in it,  a
> dual. Is that what yours is?
> There's apparently some sort of a problem with mine,  as the floppy which
> was in it when I got it had been tried so much and for so long that the
> initial tracks were completely worn away,  and you could see through it.
> On perusing the service data for it,  I notice that the drive uses a bunch
> of _incandescent_ light bulbs for things like index sensor,  etc.  I would
> imagine that one or more of these is likely to be the problem.
> I'd deferred working on it because you can't do much with it in the
> computer case,  and I needed to make some sort of extension for the power
> cable to the drive, which was a rather odd connector...
> Nice machine,  in that the S-100 card cage pulls out like a drawer.  Too
> bad it's not working.
> ------------Reply:
> Lots of luck with that Persci; nice and fast when they worked, but...
> My 3s all have Tandon singles; slower but infinitely more reliable.

I do seem to remember something about the access time (?) on that drive being 
pretty quick...

> You probably know, but the controller can use both 5 1/4 and 8" drives;


> it's sometimes convenient to hook up a known good 5 1/4 drive to check out
> the rest of the system and get it up & running before you dig into the 8".
> Also makes it easier to make disks from PC images if you need them.

It's been a really long time since I played with it,  but I remember the rest 
of the system working okay,  more or less.  There's a CPU board and a 64K RAM 
board in there,  besides the FDC (which if I'm remembering right also has the 
printer port on it).  Does 16FDC sound right?

> If there's no HD you might have trouble finding 12V though & need a
> separate supply or regulator; an external powered 5 1/4 disk in a nice
> enclosure is a useful peripheral for a System3.

I suppose I could rig one up,  but I don't know about hacking together a BIOS 
for that machine.  I never did get into that stuff all that much.

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M Dakin

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