Grrr - !%#*^@# Kaypro!

Fred Cisin cisin at
Wed Aug 3 18:08:22 CDT 2005

On Wed, 3 Aug 2005, Allison wrote:
> Dave, your on track.  The CHRN vlaues do not have to corrospond
> to actual head or cylinder.  They do not even have to be in order
> on the media!   The only limits on them are R must be 1 or greater
> (less than 255).

Which creates some complications with handling 128 byte sectors (R==0).

> My favorite format was sectors 1- 9 (512 DD) on side one and
> side two was 10-19 with H always set to 0.

Easily handled by 765, but not by Int13h.

I have to be careful to differentiate which complications are
due to the FDC chip, which to the FDC board/implementation,
and which are BIOS linitations.

Nitpick: don't you mean 0 - 9 on first side?  Or did it actually have 9
sectors on one side and 10 sectors on the other?

I've seen disks with 10h and 20h in the H field.

My favorite was 1 in the H field for the first side and 0 in the H
field on the second side.

And, of course, there are some formats, such as Superbrain,
where the data (sector content) is inverted,
but the headers (CHRN) are not.

Grumpy Ol' Fred     		cisin at

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