-=> Jasen Betts said to Greg Mayman
 -=> about "SILICON CHIP ON LINE" on 06-04-04  07:51.....

 JB> with the 286 to 486  machines I've had the experience of a cmos reset
 JB> or battery failure on theey have all defaulted to A drive being 5.25"
 JB> HD 
 JB> some later machines have come up expecting a 3.5" drive dunno if they
 JB> detected it or if that's the new default.

Probably the default.
 
 JB> I guess the drive size could be probled by timing the rotation speed.
 JB> AFAIK the hardware is otherwise digitally idistinguishable between the
 JB> two drive types.

I had no trouble resetting my CMOS from 1.44m 3.5" for the A:
drive to 1.2m 5.25", and no problems on rebooting. The drives
themselves probably are indistinguishable.
 
 GM> Have you ever tried this? And does the machine accept such a disk?

 JB> the hard bit is formatting the disk... Hmm, I guess you could set the
 JB> CMOS in a working machine to 5.25" and then just use the dos format
 JB> prog with the "U" option.

I tried it and it is not quite that simple.

The MS-DOS format command checks the disk first to be sure the
parameters are compatible and refuses to format it if it is
already in a different format.

You can override this by using the command in the form
   FORMAT /F:1.2 /U   or  FORMAT /T:80 /N:15 /U

But you must reset the CMOS for the drive to 1.2m 5.25"
beforehand.

As an experiment I formatted a 3.5" disk from 1.44m to 1.2m and
back, a couple of times each way. Of course it needed a reboot
and a reset of the CMOS each time.

And the disk in its 1.2m format was readable and writeable with
the drive set for 1.44m. That's encouraging :-)

   ,-./\
  /     \ From Greg Mayman, in beautiful Adelaide, South Australia
  \_,-*_/    "Queen City of The South"    34:55 S  138:36 E
       v
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