2.4 Megabyte Floppies

[Chuck Guzis]

On 9/9/2006 at 11:26 AM joseph c lang wrote:

>They have a two speed spindle 360/180 rpm and use 500kbit mfm just like 
>8" dd disks. 2.4 meg. only works on "microcode" disks though. And they are
pretty
>scarce.

This reminds me of one of the dodges offered early on in the PC to enable a
5150 or 5160 PC to handle 1.2M diskettes without swapping the controller
card--someone offered a dual-speed drive that spun at 300 and 180 RPM (not
to be confused with the 300/360 dual-speed 1.2M drives).  Apparently it
worked, but I wondered how good the S/N ratio at the lower spindle speed
was.  For a short time, it was either very expensive or next to impossible
to get a 1.2MB-capable controller for a 5150, since the PC/AT put the FDC
on the HDC board.  The gap was quickly filled by outfits like Micro
Solutions and Sysgen (and then the Far East cloners) and the dual-speed
drives vanished.

Is the coating on the 2.4MB floppies a standard formulation?  It would seem
to be a simple matter to format these things if that were true--assuming
the drive supports writing at the lower spindle speed.  

Cheers,
Chuck