IMHO the ultimate PC drive exerciser was something called a microtest. This is a combination of hardware and software. The hardware is an 8035 microcontroller + ADC that was connected (and powered by) the PC serial port. The drive under test was connected to the PC as B: and the (alas closed, proprietary) software run (it would run on any PC compatible, IIRC the requirements were something like 256K RAM, 1 serial port, any video card, even MDA). You then selected the drive PCB and you connected half a dozen grabber clips from the ADC box to the right points on the PCB. It would then let you do all the drive alignments using the normal catseye disk but without needing a 'scope. I have no idea where you'd find one now ('On top of the small bookcase in my bedroom, under the Heathkit aircraft navigation computer' is true, but not much help). But it is something to look out for. I modified an old Amstrad PPC laptop to have a DC37 socket in the B: drive bay so I could hook up an external drive under test and use the Microtest with it. A dedicated drive exerciser that lets you do repeated seeks, etc, is useful too. In general you _don't_ need to handle the read/write side at this stage, just checking the status lines, sending step and direction signals, and if possible checking the frequency of the index pulse. Years ago I used the parallel port on a PC for this (to work with a strange drive that my normal commercial stand-alone exerciser couldn't handle), it seems to me this is the sort of thing you could trivially do with a microcontroller that has enough I/O lines. -tony