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1979 Miller Technology Z80 single board computer M-80

candrews

Experienced Member
Joined
Jan 29, 2016
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75
Location
WA State, USA
I am looking for documentation for a Miller Technology M80 single board computer. Miller Technology was little company in Los Gatos CA and the copyright on the board is 79. This SBC has two PROM sockets, one having a monitor with a label "M-80 Monitor Ver 1.1 300 Baud". It has a fair amount of RAM, a little breadboard area and looks to be a good, simple, platform. The board has a 44 pin edge connector so smaller than STD bus but i need help remembering if there were any popular 44 pin buses then or if this is proprietary. The SBC was an industrial computer designed for embedded control more than a home/hobby. According to magazine articles of the period, it could also run Wang's Tiny Basic but i am pretty sure i never had basic for this.

If anyone recognizes this board, any information would be appreciated.

thanks

Craig
 

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I don't have information on the board, but I can say that the 22/44 pin 0.156" spacing edge connector was extremely common in both commercial and in-house/homebrew control systems. Vector made a ton of car options for the 22/44 bus, and several connector options. I've got a bunch of both the cards and connectors and still use them for projects. You could (perhaps still can?) buy 22/44 pin card cages from a number of suppliers, with bussed backplanes, wire wrap/solder tail connectors only, et c.

Many of the cards I have are full of 4000-series CMOS and came as surplus in-house wire wrapped boards from CNC machines.
 
Hey, I've got one of these now, and the PS-80 too, I believe! It looks like Craig did some reverse engineering on this board and posted videos:






Mine has the 1200 bps monitor, which I will dump and upload when I get a chance.
 
Here's mine:





Broken flywire going down to the edge connector, presumably for the RS-232 level shifting someone added in the prototype area.

The PS-80 power supply:





A closeup of the PS-80's markings:



There was a Vector 22/44 protoboard that seems to be related:





All three boards came from the ewaste bin at a customer's site. No one knew of its history, but it probably came out of a lab that was getting cleaned out and repurposed.
 
Indeed! I'm waiting on an 8154 to come in for mine, it was found without the one that's supposed to be there.
 
The 8154 came in back in May, pretty sure it's a fake. I had some time to poke at the board today. It will HALT and JMP 0x0000 just fine. I swapped in some RAM from a known good S-100 board, didn't help. The INS8154 looks like it's been walnut blasted and laser etched, the I/O lines that should be doing serial I/O really don't seem like they are. I may hack a real UART in and get GWMON-80 running for easier poking at it, or just write some test ROMs. Anyway, I ordered a ceramic 8154 from the UK, apparently they were used in a bunch of systems created over there (MK14, Acorn stuff, etc.).
 
Here's a disassembly of the code. It's a very minimal monitor. It bit-bangs serial on PB4/PB5.
 

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Thanks for the full disassembly! I'd poked a little at the monitor, enough to see that it does indeed use the INS8154 for stack. It looks like the initialization of the 8154 is pretty simple, so I should be seeing the serial output pin go to a TTL level, instead of what I'm currently seeing. More evidence there's an issue with the 8154.
 
It works now!



I bought another INS8154 from the UK, as mentioned. It came in today, is ceramic just like the listing picture, and does work. There was some corrosion on the legs which wasn't mentioned, but it knocked off with a stainless steel brush, and the pins aren't weak...so I guess I'll take what I can get. Here's the board as currently configured:



I removed the 2K of SRAM as part of debugging the dead INS8154. The Miller ROM monitor doesn't need it, it uses RAM in the 8154 for stack and variables. Here's the dead INS8154:



It's clearly laser marked, and does not match the listing picture. The counterfeit came from eBay, seller ID joma0818, and cost a bloody $37.20 shipped. I bought from a US seller thinking there would be a lower chance of getting a counterfeit, especially since the listing image showed a properly marked NS part. So much for that. This is the one I purchased that did work:


No affiliation with the seller, just apparently counterfeits are a problem for this oddball? So I figured maybe it'd be helpful to have a link to known-good chips.
 
I had some socket problems with the 2114 SRAMs. Junk single wipes, not a huge surprise. I decided to make life easy and completely strip the board. That will let me not only replace all the single-wipes and junk TI low profile sockets with machine pin sockets, but it also let me scan the board in at 600 DPI for easy reverse engineering. Click the images for full resolution:





I'm going to mess with it in The GIMP and see if I can produce blue/red copper layers and maybe a silkscreen layer. I don't plan on doing a reproduction of this board.
 
I received quite the surprise this morning when Mr Miller emailed a M80 schematic to me! It is hand drawn on grid paper and dated August of 1979. I will pass it along as soon as I get confirmation that I can share & publish.
 
I received quite the surprise this morning when Mr Miller emailed a M80 schematic to me! It is hand drawn on grid paper and dated August of 1979. I will pass it along as soon as I get confirmation that I can share & publish.
Wow, nice! Did you end up getting permission to share?
 
Wow, nice! Did you end up getting permission to share?
I didn't hear back either way.

You can find the schematic here (with the photos) also look at the very bottom of the listing at the 80 Microcomputing March 1982 document which has a schematic:

regards.
 
Excellent, thank you! I've been working on building a proper home for my M80, getting close to starting to actually wire the card edge sockets up.
 
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