Floppy drive pin 2 question? - test-drb@ccmp.vtda.org

11 Mar 2005

Randy McLaughlin <cctalk at randy482.com> wrote:

...
  Pin 2 on a 34 pin floppy connector is a little used
pin.  It was used to 
 change the RPM on some 5.25" 1.2mb drives.

 It changed the RPM from 360 RPM (pin 2 high) to 300 RPM (pin 2 low).  This 
 was supposed to make it easier to read/write DD disks in a HD drive.

 Only early AT controllers needed it, later controllers kept this pin high 
 and used an odd transfer rate. 
Hmm, my understanding is that pin 2 is LOW when the odd 300 kbit/s transfer
rate is used, and all HD drives use this pin to switch the write current
to produce the 300 Oersted field necessary for DD media or the 600 Oersted
field necessary for HD media.

MS