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