N* Question

Steven Hirsch snhirsch at gmail.com
Mon Apr 5 13:28:56 CDT 2010

On Sun, 4 Apr 2010, Steven Hirsch wrote:

> I am working at bringing up a N* Horizon system and have some questions. At 
> present, I don't have any system software and am attempting to determine 
> basic functionality.
> The box currently has a Z80-A CPU card, HRAM64 memory card and an MDS-AD3 
> hard-sectored floppy controller (others have been removed temporarily). There 
> are two built-in SA-400 SS 5.25" drives.
> Other cards that came with the unit include a Compupro bus terminator, A 
> Morrow Disk Jockey 2D/B 8" controller and a Morrow HDCA-4A hard disk 
> controller.  Unfortunately, the 8" Morrow hard disk emitted some magic smoke 
> at power up and I have not done any further troubleshooting yet. Anyone know 
> anything about Memorex 8" drive mechanisms?
> At power up, the system tries to boot the first floppy drive, then gives up 
> after 10-15 seconds.  I take this as a sign that some life exists. Then, I 
> connected a PC running ProComm Plus to the left serial port, but cannot get 
> any reponse or output there.
> So, problem 1:
> Where are baud rate settings documented?  I can find pinouts for assigning 
> signals on the DB25 connector, but not a mention of baud rate.
> Is it possible to obtain any sort of monitor prompt in the absence of a 
> booted system?  Doesn't the floppy controller have some sort of ROM monitor 
> on-board?
> Any tips for getting a terminal connection operational?  I have played with 
> handshake signals a bit, and it sure looks like both parties have the 
> necessary lines in the necessary states for communication to occur.

Following up my own post:  I did find the baud rate jumper hiding in plain 
sight on a different page of the backplane manual.

I've also concluded that there is no reason to expect a monitor prompt 
from the system, seeing as there is no monitor ROM.  I did not realize 
that the disk controller PROM is only a rudimentary bootstrap loader :-).

I'm planning to populate the EPROM option on the CPU card and install a 
copy of Dave Dunfield's little transfer program to see if I get things 

Still do need some information on the Memorex drive mechanism.  It was 
sold as a Morrow M-20 disk system, but I cannot find a shred of 
information on the drive itself.



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