<snip> Having worked on a number of those HDDs and FDDs my recollection is the "standard" for asserting READY was, at a minimum, that a disk was loaded and the drive was "at speed." In some higher end HDDs I seem to recall that it was not asserted until the heads were at TRACK 00 but I could be wrong. Speed tolerance was pretty poor with ac motors and I think we just clocked a retrigerable singleshot with index and required two (or more) indexes faster than the timeout before we then asserted READY. There was probably a pot on the singleshot and I suspect it was set to about 90% of nominal RPM for ac motor drives and probably about 2% for dc motor drives. The only real issues with motor speed not in range are writing out of sector/track boundary (high speed) and read data recovery. With today's good channels read data recover should not a problem over a wide speed range but with the early primitive channels (e.g. "two time constant") this could be a problem. Tom