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Litton Monroe OC 8880

Monroe computer

This computer came my way in 2013, unfortunately without software.
With it came also a Luxor MM1815 monitor (standard 15 inch amber monochrome monitor)

As it is with equipment that has not been on in many years 3 capacitors blew. After replacing those everything seems to work. It spins the floppydrive and displays "R1‑03 Ready for disk.".

Inside is a stamp "1982" probably production date, some IC's are datemarked 8201 too. The keyboard has Swedish characters and there is a 4KB EPROM "SWEDISH" on an extra card, character generator. So it is probably originally bought in Sweden.

I find 7 banks of 8 TI TW4116-20 16K 1bit DRAMs probably 112KB general RAM
1 bank of 8 intel P2114-4 1K 4bit SRAMs probably 4KB display RAM

So what is this, from what I can find out from internet it should be a CP/M machine. Having 128KB architecture where most of it is RAM would make it CP/M-ish.
Jan Söderberg's website? monroe.html (external) (remains of a deleted website?)
Old-computers museum OC-8880 (external) (hope this link lasts)
Anyway the sites you would find searching with google...

It is claimed to be Z80. This is not apparent. There are several 40pin Zilog components but none have the normal codes for Z80. There is a 2KB EPROM without sticker but is written 8880 on. And yes it contains Z80 code: here is a partially decoded disassembly of it MONROE.ZASM
So it seems all hardware is controlled by IO except for display memory at 3000-3FFF (4K).

My impression is that the EPROM is just hardware initializing and testing. Transferring control to an operating system found on floppy. There seems to be no drivers or something similar to BIOS functionality. So the floppy needs to contain a CP/M compiled for this specific machine.

On the "CPU card":

FD1793Floppy Interface FDC.
10168 SL0230maybe Z80
30011 SL0224?
10167 SL0226?
30013 SL0215?
30012 SL0216maybe Z80-SIO
30014 SL0225maybe Z80-CTC

On the "display card":

MC6845display controller

A graphic representation of contents of the character generator 4KB EPROM:
Chargen contents font
As you see there is both international and Swedish character sets.
On the same little card there is a jumper to select what set is in use.
The jumper seems to be in the position for Swedish character set.

I have now got two floppy images but have not been able to boot any of them. The image files look good, they seems contain DR CP/m. A PC may not be able to write them, the format is not in the PC's repetoar. Also it is possible the micropolis full size drive is not working. I'm working to verify both drive and floppies. If floppies are bad I should be able to write them with other non-PC computer.

Anyway, interested more floppy images and more information etc. please .

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