4 floppy disk drives on a PC?

[Fred Cisin]

On Mon, 17 Jan 2005, Jim Leonard wrote:
> Yep.  DOS had only one quirk, though:  If you wanted to format a 720K disk in a
> 1440K drive, you had to specifically tell DOS to format as 720K.  Otherwise, it
> assumes you're going for 1.4, attempts it, and fails.  You can choose /f:720
> with later versions of DOS; use "/t:80 /n:9" for 3.x.

To add to the fun,...
SOME drives had a media sensor that would adjust the write current for HD
diskettes, others required that come from a signal from the controller.

The early PS/2 drives did NOT have a sensor.  They would "successfully"
format a 720K diskette to 1.4M.  (Reliability was less than perfect due
to 600 Oersted v 750 )  But then, when that disk was put into a
drive that had a sensor, the drive would have problems with it.