SORD M68 without keyboard

[cjs]

FWIW, I've started setting up a repo for reverse-engineering of the Sord M68.

If anybody else wants access to commit stuff to this, just PM me with your GitLab username.

 

[tunozemichan]

The RetroStack board is fantastic! When I dumped the TMM333P BOOT ROM, I ended up using an Arduino MEGA after some trial and error. I wired everything on a breadboard and it worked out in the end.


As mentioned in the Technical Reference, the M68 motherboard is actually a two-level stack, and the BOOT ROM is located on the first level — the main board. So if you don't remove the second level (the GKB board), you need to be careful about the height of the replacement ROM. That said, even without the GKB board inserted, I believe the system still works fine — you just lose access to the graphic mode.


I've uploaded a dump of the BOOT ROM along with my Ghidra project (which I use for analysis.https://ghidra-sre.org/) to Google Drive:
https://drive.google.com/file/d/1gSq4770S02oX_BG-8_BPnCsZyiGgndR8/view?usp=sharing


The technical reference provided by @mk2s was incredibly helpful, and thanks to that, I've been able to analyze most of the parts I was curious about.


During the analysis, I found that under certain DIP switch configurations, some output is sent through the serial console — though I’ve only looked into that roughly. I also noticed that the BOOT ROM writes values to a few I/O ports that are marked as reserved areas, which was interesting to see.

As for tmon, I find it interesting to see nostalgic names like the FM-7 and JR200 mentioned.
The idea of connecting a serial ROM is really intriguing. Right now, I'm reverse engineering the memory card circuit. Once that progresses a bit more, I think we’ll have a clearer understanding of how the M68’s memory bus works.


It might even be possible to create a custom board with a serial ROM on it. Ultimately, I’m aiming to build a LAN card for the M68.

 

[tunozemichan]

I'm writing a blog post in Japanese about the initial setup for analyzing BIOS and BOOT ROMs using Ghidra. I hope it can be of some help to someone.
https://tunozemichan.hatenablog.com/entry/2021/06/01/192409

 

[tunozemichan]

I just ported CP/M-80 to the SORD M68. I've confirmed that characters can be displayed on the VGA screen and that input works with my custom keyboard. All that's left is to write the wboot code, and it will be complete.

 

[tunozemichan]

I've finally—and I mean finally—managed to create a USB keyboard adapter for the SORD M68! It's not quite perfect yet, but it's working with F-DOS and my own port of CP/M80.
Unfortunately, it doesn't work with the official CP/M68K, since that version has some unusual keyboard driver behavior, and I haven't tackled it yet because the BIOS code is unknown.
That said, since CP/M80 lets you run the MC68000 anyway, there's really not much point in getting the ridiculously slow CP/M68K running on the SORD M68.

Right now, I'm working on an integrated PCB that consolidates all the separate boards.
I'm planning to release it on GitHub. With the VGA adapter, USB keyboard adapter, and OS (CP/M80) now all available, I believe that even owners who only have the base unit will be able to enjoy the SORD M68's truly unique and fascinating design—a fully independent dual-CPU machine with both Z80 and MC68K!

 

[tunozemichan]

I’ve published a blog post describing how I built a USB keyboard adapter for the SORD M68. It includes links to my GitHub repository with the schematic, firmware, and other related resources.

https://tunozemichan.hatenablog.com...1*cw7tuf*_gcl_au*MTY5Njk4OTgyNS4xNzYxNzg2NDY4