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SC84 computer

Collection of information and attempts to recreate the firmware

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Someone asked if anyone had the firmware for this. I collected the articles and some newsletters. The MCOS firmware was in a newsletter, so I OCR'd it and recreated a source code file. Some OCR errors may be in there, but it is a good start to seeing what it does.
Then Wim Verstrepen joined the project and provided images of the firmware, software, and top-quality images of his boards.
I have disassembled the OS and the font ROM data.

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SC84-MCOS-from-disassembly-source.txt

The OCR bytes disassembled and reverse engineered into a form that re-assembles into the OCR bytes.

plain - 33.15 kB - 06/17/2022 at 22:32

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diff-memdump-bytes-and-OCR-bytes.txt

Differences between memdump bytes and OCR bytes. There are some, but not due to OCR errors. Probably due to self-modifying code.

plain - 611.00 bytes - 06/17/2022 at 20:12

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SC84_MCOS_from_memory_dump.txt

Source code recreated from hex data from a live memory dump.

plain - 14.56 kB - 06/17/2022 at 20:05

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SC84_MCOS_from_memory_dump.txt.hex

A hex file for comparison with the OCR bytes.

hex - 5.51 kB - 06/17/2022 at 20:05

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SC84-MCOS-from-OCR-hex-source-txt.txt

Source code recreated from hex data from OCR scans from newsletter. First 18 bytes disassemble to a copy-and-jump routine. Scraps of source code from various documents.

plain - 19.37 kB - 06/17/2022 at 20:05

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View all 48 files

  • 1 × MK38801 Mostek Serial, Timer and Interrupt controller chip.

  • Project Journal

    Keith03/20/2021 at 15:29 0 comments

    2020-06-28

    Started project.

    2021-03-16

    Wim Verstrepen joins the project. He has a working machine.

    2021-03-19

    Wim uploaded binary images of the CPU and VDU ROM. Hex dump of the CPU ROM exposed a couple of errors in my newsletter OCR (E with bottom missing wrongly guessed be F, and an 8 was misread as a B). The code starts to differ significantly after about $0x065B, so I assume they are two different versions. Thus I cannot verify the rest of the newsletter version. The good news is that a known-good working version has been captured for posterity. Three cheers and beers to Wim!

    2021-03-20

    Wim uploaded some excellent high-res photos of the board set. These now replace the low-quality magazine scan pictures.

    I need to find out how to have more then six pictures in the gallery. Other people have more, so it is possible.

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Discussions

electrosys wrote 12/31/2021 at 17:41 point

Contact me by email and I can let you have just about everything you want - I may have to trawl through old HDD's for some of the stuff, but I throw NOTHING away. Newsletters, listings, disassembly's etc.  I have all software for the Z80 version - I had no need for the 64180, but have a disk John Adams sent me with MCOS/SCIDOS for that CPU.  He also confirmed by email at that time that all SC84 software should thenceforth be considered Public Domain - just in case that's of interest. Regards,

  Are you sure? yes | no

Paul Williams wrote 11/03/2021 at 23:11 point

Keith, I have a print out (on continuous listing paper) of the Z80 MCOS.ASM done on a dot matrix printer in about 1985.   I have over the years tried to text process this, but I was too impoverished at print time to afford a new print cartridge and my Adobe Acrobat OCR now consistently fails to read the text. You have had an excellent bash at the disassembly of MCOS, but would you find John Adams' original labels & comments useful? I find the most legible copy is via the 'photo' setting on my scanner, so file would be quite large and some of the text at pages start/end runs over the paper perforations. You interested?

I also have some floppy disks; the remnant of my SC84 is such that I cannot read/copy them - but could you? 

Paul

  Are you sure? yes | no

Keith wrote 11/04/2021 at 01:23 point

The scans would certainly be welcome. I have no SC84 machine, but Wim has. Perhaps he could read them for us.

  Are you sure? yes | no

mister35mm wrote 03/19/2021 at 23:02 point

I have a pile of documentation from the original Powertran PSI-COMP80 computer, and the user club newsletters, and some software on a small number of cassettes.


https://www.ebay.co.uk/itm/Powertran-PSI-COMP80-Z80-COMPUTER-TECHNICAL-DOCS/402555863609

  Are you sure? yes | no

Keith wrote 03/20/2021 at 21:55 point

Thanks for the tip.  I'd scan the lot as a service to fellow techno-historians but the postage alone is about what I would pay out of my own pocket. You could try my local computer museum but museums have had no cash coming in for about a year. Likewise most people.

  Are you sure? yes | no

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