jwstephens at msm.umr.edu
Sat Nov 25 05:27:54 CST 2006
Dave Dunfield wrote:
>I have many images for both single and double density Horizon systems on my
>site - if It's SD, your choices are NorthStar DOS and my own DMF system. If
>DD, the choices are NorthStar DOS, CP/M and UCSD Pascal.
>But you will have a bit of a "chicken and egg" problem - the NorthStar disks are
>hard-sectored, which means that you can only make them on a system with
>the NorthStar controller. Unless you have other N* systems kicking around
>you will have to use the Horizon.
thanks for mentioning your site. I knew someone had some material
online, and it is probably you
I was thinking of.
As to the chicken or the egg, I took the approach of getting the bios
code to run the horizon
controller, and generated a horizon CPM that would run one of my Tarbell
controllers in the
box with the Horizon controller. it only took a bit of editing to boot
the cpm with both, and
it would sysgen and format either diskette, 8" or 5 1/4" and also run
pip for copying
data to and from each format. I just split it up so I had 2 drive
letters for each type, so
A,B was one, and C,D was the other.
I flipped the code and merged the horizon code into the tarbell code later.
I don't recall back then as to my chicken and egg problem which was how
to get the sources
needed to do the tarbell onto the horizon, but I think I captured a
listing via a serial program
and edited the tarbell bios stuff into the cpm on the horizon. After
this bootstrap, which
involved maybe a hundred lines of code, I could merge up enough to do
diskette, then finish.
Now, if you have access to moving data from a simulated CP/M to 8" and 5
could do the editing anywhere, and go back to the 5 1/4".
but someone has to bootstrap you onto the 5 1/4" northstar, since it is
pretty much one
of a kind.
many different ways exist onto 8" but the problem dave mentions means
you have to
start up somehow with a few 5 1/4" diskettes, and generate your boot,
and I assume
a way to assemble, test, then use the horizon bios, so you can adapt
what you need.
The only thing that a true horizon has is a 256 byte boot, and I don't
know of anything
that does anything but floppy booting exists.
I remember the boot rom gets mapped into somewhere in the Exxx range,
in a 256 byte sector, then jumps to it, before going away. I don't
think you could
pull it and get a serial program into it to read one of the serial
ports, but I won't say
never to the crowd on this list.
And my memory of 256 bytes may be off, I vaguly recall maybe on 32 bytes
and used by the processor at boot. People had to use pretty small proms
in the early
days of the hobby.
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