On Mon, 5 Jan 2004, Pete Turnbull wrote:
> On Jan 5, 15:02, Gene Buckle wrote:
> > Me, I want to know how they make an FM/MFM drive read a GCR disk...
> It's not a drive issue, it's a controller issue. The bits on the disk
> are just bits on a disk... just alternating magnetic poles. There's
> nothing strange or different about the heads or amplifiers on an Apple,
> Commodore, or Amiga drive.
... but the controller is ALSO FM/MFM. THAT is the "impossible" part.
hint: disrupt in mid-read by messing with drive select
and some drives work easier than others for it. For example,
with the Apple Turnover, Tandon TM100 drives worked well,
but Teac 55's would often not work without some minor mods.
Long ago, I tried unsuccessfully to implement the technique.
And then more recently, I tried some software that purported
to do it. Also unsuccessfully.
But neither of my attempts were in sufficient depth to state
that the technique can't work - my congratulations to the guy
who succeeded!
And once there is a successful track read, parsing sectors
and working out the DIRectory is straight-forward.
--
Grumpy Ol' Fred cisin_at_xenosoft.com
Received on Mon Jan 05 2004 - 17:54:18 GMT