CP/M

From: Don Maslin <donm_at_cts.com>
Date: Fri Jun 19 14:14:58 1998

On Fri, 19 Jun 1998, Pete Turnbull wrote:

> > 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 ?

Yes, I have several FDCs with the 8473 chip and they do the deed nicely!

                                                 - don
 
> > "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 - 14:14:58 BST