DEC RC25 Drives

From: Ethan Dicks <>
Date: Wed Feb 19 12:33:00 2003

--- Owen Robertson <> wrote:
> A few weeks ago, I got a rather nice PDP-11/34... I also got
> two RC25 drives, along with controllers and cables. I've never seen these
> before. Can anyone tell me anything about them? They look like nice
> drives, but I've never really heard much about them.

The controllers should be "KLESI/U" - an intellegent controller that,
I think, should be able to talk to a model TU-80-something (not a
straight TU-80 - that has formatted Pertec I/O over two 50-pin cables,
IIRC) as well as the RC25 drive. Not sure if the controller can talk
to more than one device at a time, though.

You will not be able to spin it up without the removable cartridge.
It has one motor and one positioner, but 50% of the storage is
enclosed in a white disk pack several inches on a side and about 1/2"

I used to have one, embedded in a VAX-11/725, but it was on loan when
the borrower's company was sold. I heard about the relocation too
late. :-(

I never had a problem with them, but I keep hearing horror stories from
others. They are *not* high performance disks.

The last time I saw one used in a production environment was well over
10 years ago, as the boot node for a small VAXcluster. VMS 5.0
fit on one, barely. Never seen one attached to a PDP-11, but there's
no reason why it shouldn't work. I just don't think people were
buying too many Unibus PDP-11s when the RC-25 came out. If you
were going to spend real $$$, you'd probably have bought a UDA-50 and
a "real" MSCP disk, or replaced the Unibus stuff with a MicroPDP and
some flavor of RD5x drive (or in the case of one of my clients in 1986,
an SMD controller and a Fuji SMD drive, if you didn't have a 100% DEC

Probably plenty of room on them for RT-11 or RSTS. Don't know where
you are going to find cartridges these days, though. Perhaps the
usual suspects (Keyways, Continental Computer, Newman, Computer
Clearing House...)

Received on Wed Feb 19 2003 - 12:33:00 GMT

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