> I think that there are some exceptions to that Tony. The following is a
> clip from some correspondence with Chuck Guzis at Sydex a while back:
>
> "Another topic that I'd like to see some commentary on is how people
> have handled those old diskettes that lack the Index Address Mark
> information, such as those used on the Cromemco C10. On a PC
> controller, the first sector on a track on such a diskette usually falls
> to be seen by the FDC because it falls in the "blind spot" (ostensibly
> PLL sync-up time) of the 765-family chip.
Have you tried using a controller that doesn't need the Index Address Mark,
such as a WD1772 or a NatSemi DP8473 ?
> "But 3.5" diskette drives are too difficult to modify. We've had good
> read and write results by passing the index signal through a 1-shot
> carefully adjusted to trigger slightly ahead of the actual index
> position. But this is a very touchy arrangement, though it does work.
But the Index Address Mark isn't part of the spec for 3.5" disks. I know
most PC controllers put it there, but it's not in the Sony spec, and some
controllers (see above) will work fine without it.
> I know that I have experienced the problem of the first paragraph on more
> than the C10 disks.
> - don
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Received on Fri Jun 19 1998 - 02:43:25 BST