Floppy drive pin 2 question?

[Fred Cisin]

> > 2.88 mb controllers use it one way, some 1.44mb drives use it
> another, some
> > 5.25" drives use it for one thing other another.

On Mon, 14 Mar 2005, Pete Turnbull wrote:
> 1.44MB drives, ie 3.5" drives, do not need to be told what density to
> use; they use the media sense to detect that from the holes in the
> diskette.  Therefore if they use pin 2 at all, they usually use it to
> signal to the controller whether the media loaded is HD or DD.

On the early PS/2s, IBM used both 720K drives, and ones that they called
"1.44M", that held 1.40625M (2*80*18*512)
Unlike everybody else in the world, IBM did NOT have a media sensor!
... and therefore used pin 2.

Using a 720 K diskette in one of IBM's 1.4M drives resulted in a not very
reliable 1.4M.