Diablo disk unit

It appears to be a standard Diablo model 30 disk drive. This is a front loading hard disk, similar to an RK05, in fact it was used on the PDP11 with the RK11-C (but not RK11-D [1]) controller. There are 2 versions, low and high density, which DEC badged as the RK02 and RK03. The latter is format-compatible with the RK05, the former (which is much less useful) has half the bit rate. It needs an external +/-15V power supply (I can't remember if it needs +5V too). [1] It uses 1-of-n selects, not the binary select scheme used by the RK11-D. It is possible to kludge in a decoder to get the high density model working on an RK11D. AFAIK the RK11-C supports both data rates, the RK11-D doesn't, so the low density version is pretty much RK11-C only. One oddity is the head positioner. It's a permanent magnet commutator type motor with a rack and pinion mechanism. -tony