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This mini forum is intended to provide a simple means of discussion about the Litton - Monroe OC-8880 computer. If you want to share your own experience or memories, or add relevant information about this system: post a message!

  Click Here to add a message in the forum


Saturday 6th June 2020
Knut Roll-Lund (Norway)

Hi again all. The teledisk images have 16 sectors per track this makes them 360K. This makes them DD (Double Density) which is why I could write them on a PC with a 1.2MB drive.
The Micropolis 1015-5 in The OC-8880 is a QD 400K it seems to spin at 300 RPM but should have 20 sectors per track and 80 tracks. I thought 5,25" QD would rotate at 360 RPM similar to 8" so clock would be double of DD. I don''t know if it has two speeds and actually boots at DD and 300 RPM but can also do 360 RPM and QD.
I wonder if QD would be similar to HD and use a significantly higher current to write (bias) like PC 1.2MB does.
I will proceed to look at the floppies on another computer to see if there is anything sensible there. Also check frequencies on FDC and CPU to see if that makes sense.
The drive seems OK, though rotating speed may be a little off, if other things are OK I will try to adjust that.

Thursday 28th May 2020
Knut Roll-Lund (Norway)

I tried the TeleDisk images Alejandro Daniel Perez found. Unfortunately no success yet.

I created real media with ms-dos on a 1.2MB 5.25" drive (has 80 track) and used DD 360K media, though it is not certified for 80 track. This seemed to go well, so far so good.

The OC-8880 did respond with some more messages so it was trying. Loading, but didn''t like the floppy. From the sounds the drive may be bad.

I will try to find out if the floppies are ok on a different old computer. I will try to find out if the drive is bad, if it is an 80 track drive etc. In 1981/1982 80 track wasn''t that common. Two years later it was pretty common.

BTW I will try mesuring what frequency the CPU has, and confirm if signals match Z80.

Thursday 16th April 2020
Alejandro Daniel Perez (Argentina)

Hi everyone! I believe that I have found a disk image to check with this computer here:

The image name is monroe.td0 and monroe88.tdo, if anyone can check it I would like to know if the images are working fine. I have a Monroe OC-8820 but it still under repair

Friday 16th August 2019
Nils H (Sweden)

The Monroe OC8800 could probably run CP/M, but it was offered with another operating system called OS8MT which was a multi-tasking 8-bit operating system.

There was a Basic interpreter that is related to the Luxor ABC800 series computers and the Diab Basic on the Motorola Unix computers.

There''s even an MS-DOS version of that Basic named basic2pc. There are however some differences in instruction set, but those differences are minor. Search for BASIC2PC.ZIP to find it. The basic is a semi-compiling basic which makes it fairly fast when executing.

One Monroe-specific instruction that I happen to remember is "OPTION EUROPE", which allowed you to programmatically determine if there should be a comma or dot as decimal separator.

Sunday 1st November 2015
Knut (Norway)

Stefano''s link is now broken. I had to move my site, so the link should be and yes the 2KB EPROM is correctly a dump of the boot ROM of the OC8800 but it contains only initialization and ability to load and execute a bootsector from a floppy. Not very useful if you don''t have a bootable floppy for this computer (probably CP/m). I have the machine but no floppy...

Tuesday 29th July 2014

The MESS project claims they need its ROM dump.
Pehaps the 2kb image in this link is useful ?

Thursday 10th November 2011
Bob Hall (usa)

The OC8800 and 8820 were manufactured in Monroe''s plant in Lexington South Carolina. This was the first of two attempts of Monroe to enter the desktop computer business. Operating memory was either 256k or 512K. dual 6" floppies and optional 5 or 10 Megabyte external hard drives. The model shown was intended as a system dedicated to educational use. This incorporated early verisions of software to allow a student to draw and color objects. The acutal commerical version was a single cabinet design with a 80 column dot matrix printer using 4" calculator rolls the display was an orange monochrome 8" monitor.

Saturday 24th February 2007
PeriSoft (New York, USA)

Gotta love the lace doily under the monitor. Classic!

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