Re: Northstar Horizon and Socor IQ130 HELP

Well, you have a non-standard configuration.

The Northstar disk controller has been removed and replaced with the
disk jockey. The two are radically and dramatically different in every
regard. The DJ won't run the NorthStar DOS, and the NorthStar won't
generally run CP/M (but there were versions of CP/M that were adapted to
the NorthStar controller, with some limitations because the NS
controller had a ROM and hardware I/O addressing that limited the size
of the CP/M TPA).

This also means that the boot rom in the computer won't boot the system,
because it was a NS boot rom that expected a NS disk controller.
However, the ROM may have been modified to support the DJ, or it may
have simply been disabled so that the DJ could use it's own boot mechanism.

No - the Boot ROM for the standard Horizon is contained on the NorthStar
disk controller - the ZPB has jumpers to set a power-on jump. This is normally
set to E800 for the double-density controller or E900 for the single density
controller, however it can be jumper configurable to any memory block.

I am not familier with the Disk Jockey, however assuming that it has a boot
ROM, it is quite likely that the power-on-jump has simply been reconfigured
to execute the DJ boot rom at power-up. Hopefully it's in a better place than
the NorthStar ROM (ie: not in the middle of the memory map) and if so, the
HRAM card has likely been configured to provide a full RAM configuration
fitting around the disk controller ROM (all conjecture on my part).


But the real problem is that the configuration, whatever it was, is
completely non-standard, so you can't rely on ANYTHING. And the 2nd
problem is that you don't know what works and what doesn't, and in a
system this old, there are likely multiple boards not working (in fact
it would almost be surprising if any of them worked).

I don't think that there is ANY way of fixing this unless you have
another system in which you can test and repair the boards
one-at-a-time. There are simply too many issues here to deal with when
you know nothing about the system configuration except that it is
non-standard, and when it's likely that there are multiple fatal problems.

I disagree with this - You just take it one step at a time. The fact that
it accesses the drive on power-up tells me that a fair bit is working
at least to some extent. The CPU is working, the disk controller is
working at least to the point where it can access the drive. Most likely
the RAM is working as it has probably used stack to get to the point
of booting, however you could pull the RAM card and verify that it
does not access the disk to be certain of this.,

I have the docs for the NorthStar cards and backplane on my site.
With these you can determine exactly what addresses are used,
and exactly how the I/O has been setup.

The ZPB has an option to put a 1K ROM on the CPU - One thing I
might do is to drop in a little "ramless" Z80 monitor program that
talks to the Horizon serial console - with this, as long as the CPU
and mainboard are working you can poke around from inside
the system. If not, then you have vastly narrowed the field of
debugging, once you get the ROM executing, the system will
sit in a UART polling loop, and it's just a matter of tracing the
signals.

If everything seems to be working correctly but you can't talk
to it, it may be your terminal - use a light box to check for data
going back and forth, and try a PC as a terminal.

With the monitor, I would then checkout the RAM - try writing and
reading from it and see if it works. I would also extract the content
of the disk controller ROM and disassemble it to see exactly
what it is doing, and where it is trying to load the boot sector.

Assuming all goes well, I would launch the disk ROM, then
reset the system and look to see if anything was loaded. If
you had do, you could patch a new copy of the ROM to jump
back to the monitor after loading the boot sector. Track
down and fix hardware problems as necessary until you have
a good boot sector load.

This is all assuming you have a good boot disk for that controller.
If you don't know, then make a cable to connect the drive to your
PC and use my ImageDisk utility to read the disk into an image file
on the PC (assuming it's soft-sector). Then you can verify that the
disk format matches the controller setup in the DJ boot ROM that
you have disassembled, and that the boot sector looks like it should
work with that controller/ROM (more disassembly required).

Once everything works, then you should observe the drive load the
boot sector and step to the next track - possibly further. If the drive
- recalibrates to track 0 (manually move it out with the power-off
to confirm this)
- Loads the boot sector
- then steps out one or more tracks
the controller is likely reading the disk OK - since we have already
gotten the console to work, if you have a good boot disk, you
may get the OS prompt. If not, more disassembly and debugging.


If you do have another system, the first task is to test the CPU and
memory boards, then the disk controller. Once you know that all of the
components work, you can put them together and try to make a working system.

Also, since the system is totally non-standard, you will need a custom
BIOS, and again it's really tough to create one unless you have another
working system on which to do it. Plus you have to know 8080 assembly
language programming and have enough hardware information to write the
custom BIOS.

Yes, but again not impossible - by putting a monitor on the CPU card, you
can effectively give yourself a front panel - with the ability to load programs
into memory from the monitor, you CAN create a custom disk without
another system.


to the OP:

If you know what you are doing, all of this is actually pretty straightforward.
If you don't - then you will learn a lot and probably have some fun (if you
like these sort of challenges). If however, you are looking for a "plug and
play" solution - then we don't have one for you.....

The beauty of these old systems is that are actually quite simple, it is
possible to determine and understand the complete boot sequence from
RESET to OS-prompt. It will take some work, but it can be done, and can
be a very rewarding experience.


Regards,
Dave


--
Dunfield Development Services http://www.dunfield.com
Low cost software development tools for embedded systems
Software/firmware development services Fax:613-256-5821

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