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

Ethan Dicks ethan.dicks at
Thu Jun 4 19:49:33 CDT 2015

On Mon, Jun 1, 2015 at 1:09 PM, Robert Armstrong <bob at> wrote:
>   If you actually get an RC-25 drive working, I'd love to hear about it.  I
> have three RC25s (one actually in my 11/725 and two spares) and none of them
> work.  They were never very reliable drives, even when brand new, and are
> possibly the worst drives DEC ever made.

Ain't that the truth.  I had a 11/725 with a working RC25 back in the
1990s, and I've semi-recently replaced it with a different 11/725 that
did not come with a removable cartridge so I've not been able to spin
it up to test the internal platter.  Hopefully it works, but if it
doesn't, (see below).

>  Fortunately for an 11/23 or 11/83 there are lots of alternative drives available.

There are.  Unfortunately, for Unibus machines (11/725 especially),
there are not as many alternatives.

One I've seen is to nibble a chunk out of the rim of the cover skin
(to prevent pinching) and run a BC-11-A Unibus ribbon cable out to a
BA-11 and stick any number of controllers in that, such as an
easy-to-find-but-power-hungry UDA50.  Also good for adding more
serial, etc.  Just put RAM in the CPU box and leave all the
peripherals in the external BA-11.  Not supported by DEC, but it works

I've also heard of people using Emulex and other 3rd-party SMD and
ESDI controllers.  Those aren't too expensive.  Unibus SCSI, OTOH, is
not common, but a joy if you can find one.


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