Northstar Horizon

Dave Dunfield dave06a at
Sat Nov 25 10:17:58 CST 2006

> 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, 
> and reads
> 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 
> are visible
> and used by the processor at boot.  People had to use pretty small proms 
> in the early
> days of the hobby.

I provide a couple of images with my tools, which include the NorthStar
DOS and the serial client in one binary image that you load at $2000
and execute - it will then communicate via serial with the PC side of my
program and allow you to download disk images directly to the drive.
I include the serial I/O portion in source so you can customize it to
different serial I/O if required.

So ... there are basically two ways to get the system up and running:

1) you have another S-100 crate, and can make 1K free at E800-EBFF, then
you are laughing, as all you need to do is install the N* controller, load the
client code under whatever system you have running, and launch it.

2) If you don't have another system running, then you need to bootstrap the
client code into your box. If you have a box with a front panel, then you can
toggle in a small loader to load the client. If you have a faceless box (like a
Horizon), then you need to use a ROM monitor to load the code. I have a
couple of tiny monitors which has enough capability to do this (my PC client
will in fact "type in" the 8080 side using memory edit commands and can be
configured for most monitors).

Many CPU cards like SSM CB2 have a ROM socket so this is easy.
Actually IIRC the NorthStar CPU has a 1K ROM socket. So all you might need
to do is put the monitor in the ROM socket and ...

The NorthStar CPU has jumpers to set the power-on-jump address, normally
this is E800 (DD) or E900 (SD), however you can set it to any xx00 block
address. So if you put in a ROM (either on the N* board or in a separate
ROM card), set the POJ jumpers to the right address and you should be
up and away.


dave06a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Collector of vintage computing equipment:

More information about the cctalk mailing list