Rescue update: DEC RC-25s + / was Re: DEC cartridge ID

Sean Caron scaron at
Mon Jun 8 15:17:02 CDT 2015

Yeah, there were a few CDC drives like that ... I encountered a few "Hawk"
drives once on an old Alpha Micro  S-100 machine long ago; I believe it
was, five megs fixed, five megs removable?

The pack was about the size of a garbage can lid and I believe the unit
spun them up to around 2400 RPM or so ...

Those are the oldest, largest magnetic disk drives I have ever seen in
operation and it was very impressive to me at the time! So loud just
running and a very definitive "clunk" from the head assembly when it
started moving!



On Mon, Jun 8, 2015 at 11:31 AM, tony duell <ard at> wrote:

> > The RC25 was one of the last cartridge drives (before fixed drives came
> back in small sizes and exploding
> > capacity), somewhat interesting because of its compact size, and very
> odd and hard to use because the
> > designers threw in a fixed platter.  Perhaps they thought that it was a
> good idea because it gave you double the
> > capacity at modest extra cost, but in practice it made for a major pain
> in the software and operationally.
> Many other compainess pulled a similar trick...
> The CDC 'Phoenix' (is that a 9648 or something) had a removeable pack
> containing one  platter and
> 3 fixed platters. Capacity was 16MBytes per surface (or so), so the
> removeable pack stored 16Mbytes)
> (one data surface, one servo surface), the fixed part was 80 MBytes (5
> data, 1 servo surface).
> Plessey made an RK05-a-like (same interface, linked to their version of
> the RK11-D, took same
> cartridges, same format, etc) with a fixed platter as well as the
> cartridge. Of course the HP7900 was
> like that too.
> I never really liked the idea. The main problem was you lost access to the
> fixed disk(s) while changing the
> removeable one.
> -tony

More information about the cctalk mailing list