CP/M BIOS setup

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Sat Oct 7 16:42:57 2000

From: Eric Smith <eric_at_brouhaha.com>

>He's not proposing to figure out the parameters by looking at tables in
>the BDOS. As you correctly point out, that stuff is in the BIOS.


True the BIOS is the repository of the disk information but it's not all
as I've repeatedly said in the "tables". It can be deeply embedded
in the code.

>Richard's point is that on a bootable disk, some set of sectors contain
>the BDOS code, which has known contents (for any specific DRI CP/M
release).
>The point is that some of the disk parameters can be worked out by
matching
>what sectors on the media contain what pieces of the BDOS code.


Sorry but the BDOS is usually in reserved tracks where things like skew
(aka intereave) is not always there or even the same density.

The BDOS other than being a known block of code contains none
of the disk specific code or layout. Putting that in the bios is what
made cpm portable to different platforms.

>It may not tell you everything about the disk format, and it obviously
>only works on bootable diskettes, but I think it is a good start.


It's only a start. to me as an bystander to this it's a interesting
exercize but one fraught with exceptions and limiations for it to
work reliabily.

Allison
Received on Sat Oct 07 2000 - 16:42:57 BST