Bringing up a CPM

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Thu May 27 15:20:36 1999

On Thu, 27 May 1999, Dwight Elvey wrote:

> allisonp_at_world.std.com wrote:
> >
> > The standard size for cpm a is:
> >
> > CCP 800h 2048 bytes
> > Bdos E00h 3584 bytes
> > BIOS variable 8"sssd example is 1500bytes.
The word variable indicated the length not the BIOS variables. Bioses for
CPM system can be very variable in size, I have one system that has a 32k
bank dedicated to the bios itself. It can be as small a few hundred
bytes plus the tables.

> >
> > This is generally stuffed on to the sssd 8" as the first two tracks of the
> > disk, 52 sectors total or 6656 bytes for all three components.
>
> Hi Allison
> This also doesn't make sense. Track 0 sector 1 is the boot loader.
> That leaves 25 sectors in the first track. 26 in the second track
> makes a total of 51. This is contrary to your example. You only have
> 6528 bytes or a little fewer for BIOS variables.
> Still that doesn't explain the 7680 bytes in the file from
> the site. I still don't know what to do.
> Dwight

The stuff you deleted and didn't copy is the stuff you should read.

The copy you have has an extended bios at the end and Nad the 128bytes for
the boot are not always there as the boot is specific to the MDS800
example. So you may be right and the first sector _may_ be the boot.
Also of the cpm system has a really large bios or the copy is a "snapshot
of the system in ram from DDT the length may be way over the top.
Simply count of from the start and allow for the boot if there. The
beginning of the bios is easy to find as there will be some 17 jumps
starting at xx00h.

I guess I can just wrap a copy of the CCP and the BDOS and send them to
you this weekend. What address do you want to start at?

FYI: cpm nominally is supplied as a 8"sssd disk with the MDS800 bios so
the manual reads right and it's sysgen'd for 20kb of ram. Other vendors
did different things that often for the 5.25" floppy case were all over
the map.

No matter what copy you use, you have to rewrite the bios as likely it
does not match your IO or disks.


Allison
>
Received on Thu May 27 1999 - 15:20:36 BST