View Full Version : Wanted: Disk Drive for PDP-11/23+

October 28th, 2010, 07:09 PM
I've been trying to find a disk drive for my PDP-11. I was hoping to find something along the lines of an RX02 or RL02, so I could have something different / interesting to use with it. I would also have to locate the appropriate controller of course. I was just poking in the dark, hoping that maybe someone knew of something out there somewhere.

I've tried the usual Craigslist and ebay, without success. If anyone has any suggestions, I would definitely appreciate it.


October 31st, 2010, 02:35 AM
The RX02's, while interesting, are a bit limited in their capacity. 512KB. . . you can still find the media on-line though.
The disk drives themeslves have become a bit scarce. You can use genuine RX02 disk drives, or if you see dual floppy chassis
marked "WT78" (which were from a DEC word processing terminal) you can use them as well. The controller is an RXV21,
which is an 18-bit controller, however some operating systems (such as RSTS) support them in 22-bit environments.

The RL01's and RL02's are really nice to have. They are built like tanks, and are easy to use and maintain.
Those are also becoming difficult to find, and at 19" wide x 10.5" tall x 32" deep, are quite large.
The RL01 is a 14" 5MB pack, and the RL02 is a 14" 10MB pack. The RL02 drive will read either media.

There are two controllers for the RL01's / RL02's . . . a 2-board RLV11 controller, which isn't particularly desireable.
(It uses the Q22/CD slots, which aren't available in all backplanes.) The RLV12 controller is what you're looking for.

The RL01/RL02 drives use special connectors. They make a cable that goes directly from the controller to the drive;
it will have a 40-pin (or 50-pin - I can't remember) BERG connector on one end, and the other end mates directly
with the drive. Otherwise, there is an odd bulkhead adapter that mounts on the back of the BA11 / BA23 / BA123 chassis,
that converts a ribbon cable (inside the cpu chassis) to an (external) RL01/RL02 connector. . . . and then you'd use an
RL01/RL02 interconnect cable to go from there, to the drive.

There are TWO of these connectors on each drive, for daisy-chaining up to 4 total drives.
Each drive has to have it's own unique drive number, which is set by the lighted plastic unit number (0,1,2,3,4 etc) on the front of the drive.
*** THE LAST DRIVE NEEDS TO BE TERMINATED, or your drive won't be recognized, or you will have drive errors during operation.)

You might want to keep an eye out for an inexpensive SCSI controller. . . at least you'll be able to find drives for them
for several more years. . . . A CMD CDQ-200/M or CQD-220/M is a good choice for low-end machines. Make sure you don't pick up
the " /T " variety (for tape only). . . MTI made "clones" of these as well, with similar part numbers. Dilog's SQ706 is OK, too.
Expect the going price for these to be around $125 - $175, depending on the mood of the market.
If you stumble across an Emulex UC07, UC08, or any of the CMD CQD 4xx/M controllers for under $200, that's a steal as well.

December 29th, 2010, 06:09 PM
> A CMD CDQ-200/M or CQD-220/M is a good choice for low-end machines. Make sure you don't pick up
> the " /T " variety (for tape only). . . MTI made "clones" of these as well, with similar part numbers.

I have had success converting CMD CQD-200/T and CQD-220/T versions into /TM versions by replacing the EPROMs with firmware copied from /TM version EPROMs. The CSR decode PAL also needs to be replaced with a /TM version. I was unable to simply copy the /TM version PAL but was able to reverse engineer the /TM version PALs and program equivalent PALs.

As far as I can tell an MTI QTS-30 is the same board as the CMD CQD-200/T and I have also converted an MTI QTS-30 into a CMD CQD-200/TM equivalent.