26 Nov
2006
26 Nov
'06
6:51 a.m.
The processor board has the provision for 1K EPROM,
which isn't installed.
I'd assume it's for a 2708 device. Unfortunately I cannot program these
devices, so I can program a 2716 and do some mods to the processor card to
make the 2716 work and show only the 1st 1kbyte.
If you don't want to modify the card, you could make a little adapter. 1K is
plenty to get the Horizon booted. All you need is something that will let you
write the boot client into memory.
I have a little 8080/Z80 monitor I could send you which fits in about 512
bytes and has the advantage that it does not require ANY ram - makes it
very nice when you are trying to figure out faulty RAM.
In my spares I have a few Dynabyte and Microbyte RAM
cards (both static and
dynamic), an old MITS 8800B CPU card (which needs some serious TLC), a spare
ZPB processor card, some weird S-100 Inc 4K EPROM card which looks like it
can take 8 x 512byte, or 4 x 1k or 2 x 2k EPROMS, a Vector Graphics ZCB
processor card, and a few S-100 blank prototyping cards and a 4-slot S-100
mainboard.
I can wire-wrap up one of the proto boards as an EPROM card if I need more
and run the DOS all in silicon, if this is possible. So, if push comes to
shove I can modify and use one of my 8080/85 debug/monitors and let it run
on the Northstar.
I wouldn't - that adds complexity of another untested card. 1K is enough to get
going and keeps things simple. If you put in my RAMless monitor, all you need
to get working in order to talk to it is the CPU (with it's ROM socket) and the
serial port. Once you are "in", it's much easier to get things working from
there.
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html