micropolis disk question

--- Ed <quapla(a)xs4all.nl> wrote: ST-506/ST412, not ESDI. The ESDI drive that looks like these is a model 1355, IIRC. I've seen the ESDI drives in old outboard Sun boxes. The 1325 can be converted to DEC use (as a 73MB RD53) by adding the infamous 0 ohm jumper at R7, then low-level formatting on a MicroVAX 2000 (using the ROM diagnostic formatter) or a Qbus MicroVAX with an RQDX3 and the Diagnostic tape formatter, or even a Qbus PDP-11 w/RQDX3 and XXDP. It large enough to run VMS 5.0 (barely) or 2.11BSD (barely) or 2.9BSD (with some room to spare). RT-11 is a possibility, too (v5.4 and up?), but you'd have to partition the drive into multiple "devices". To get to the jumper, loosen the two flat-head screws at one end of the circuit board on the bottom of the drive, tip it up (it's on a pivot), and look for R7 on the silkscreen, somewhat near the middle of the board. Solder in a jumper wire, reassemble and install! If these drives came out of a PeeCee, check the unit jumpers before putting them to use in a DEC machine. To forestall any "warnings", you will probably find that these drives do not have the best longevity. Many of them have lots of hours accumulated already. They probably won't stand up to heavy use. The bearings seem to go in the ones that I've had fail. I don't think I've ever had a head crash. -ethan