No, but 5.25" HD drives as well as 3.5" drives for the NEC 9801-type
platforms do spin at 360 RPM.
True.
I do know that fro the 600 rpom Sony 3.5" drives, the procedure for
checking the spindle speed is to measure the period of the index pulses
(it's actually physically impossible to put a srobe disk on those
drives...). I assume the same method can be used on any drive.
-tony