Is this the drive that's used in the 9153, 9154 and some Vectras? If so, then read on :-) The interface seems to be a bit strange. There are raw data lines (like ST506) for the actual disk data, and an 8-bit bidirectional data bus for control. There are also cryptically-named control lines which refer to an ADC and DAC (!). There were service manuals for the drive and/or the 9153 on hpmuseum.net, but I don't think they've been restored after the crash yet. They were, alas, boardswapper guides with no real information, apart from the fact that one of them contained a pinout, which I extracted and reproduce below. It's a start anyway. 1 Rd Data 2 Gnd 3 Wr Data 4 Gnd 5 Wr Gate 6 Gnd 7 4MHz Clk 8 Gnd 9 Rd A-D converter 10 Gnd 11 +5V 12 Gnd 13 +5V 14 Gnd 15 +12V (Motor) 16 Gnd (Motor) 17 +12V (Motor) 18 Gnd (Motor) 19 Dr Sel 0 20 Dr Sel 1 21 Dr Sel 2 22 Dr Sel 3 23 Wr D-A Converter 24 NA/B 25 Sector Pulse 26 Index Pulse 27 Wr NIC Chip 28 Reset 29 +12V (Motor) 30 +12V (Motor) 31 Fault 32 +12V 33 Data Bus 7 34 Data Bus 0 35 Data Bus 6 36 Data Bus 1 37 Data Bus 5 38 Data Bus 2 39 Data Bus 4 40 Data Bus 3 -tony