"In the case of the 1771 and 179x series it's possible to build a really neat circuit I've seen but never tried to match, which uses the /TEST pin on the FDC to cause the device to put out its pulses much faster, allowing them to be accumulated externally in a counter, which, drives a DAC which drives a VCO, which drives the counter as it downcounts the number of steps, thereby slewing the head assembly. This could lead to an interesting but lengthy discussion. " Sounds like an ideal candidate for reimplementation in a single chip microcontroller.