On 07/12/2018 01:40 PM, Paul Berger via cctalk wrote:
IBM created the 8" diskette as an inexpensive and reliable
means of loading microcode and shipped the first read only
drives in 1971.
I am quite certain the original FDD on the 370/168 used a
pair of solenoid coils to ratchet the head in and out. I
think the mechanism was a leadscrew and toothed wheel. I
heard a 370/168 loading a microcode overlay and it sounded
like a machine gun, even in a pretty loud machine room.
I think the same scheme was used in the 370/145.