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

Mike Ross tmfdmike at
Mon Jun 8 09:26:07 CDT 2015

On Tue, Jun 9, 2015 at 2:06 AM, Paul Koning <paulkoning at> wrote:
>> On Jun 8, 2015, at 10:02 AM, Mike Ross <tmfdmike at> wrote:
>>> ...
>> Ugh OK, I've never laid hands on one as I said; for some reason I
>> thought the cartridge on these was a sealed unit containing the heads,
>> like some IBM drives, e.g. 3340…
> No, and I don’t think DEC ever made any drives like that.  The removable cartridge drives are all variations on the RK05: one or more platters wrapped in a plastic shell that has an aperture for the heads to enter.  The heads are in the drive.
> 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.

Hmmm IBM used exactly the same trick - removable platter, with a fixed
platter below it - in 1969 with rather larger platters on their 5440
disk for the System/3... I have one of these; have had various things
to fix (some still unfixed!) but the disks have been entirely
reliable. Cartridges look very similar to RL02...
'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'

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