archive.worldofdragon.org

OK, don't bite me... https://docs.google.com/spreadsheets/d/e/2PACX-1vSV9pZwTCZp1znalJSEY0smTu5m1WvSgWehv29hd6jRWGaI8VGxhoWdUfvuli40WYeqLR4oHaX4lL6X/pubhtml?gid=0&single=true Hehe. A few notes on CoCoMEM Jr: Full specifications and technical info not available, but video memory access is problemmat...

For your spreadsheet: CoCoMEM Jr replicates the CC3 MMU (8kB pages, multiple tasks, optional common memory at $fexx, etc.) It currently sits in the CPU socket The HW design supports 14 bits of MMU address extension (128MB of linear address space) with 2 "special" bits reserved for memory protection,...

I think Jim Brain (Go4Retro on here) said his project does interface to video, but I can't remember how. Maybe interposes the SAM as well as the CPU. My effort is a work in progress, but it currently creates a "hole" in the address space for pages 38-3f and passes memory requests to those memory lo...

Hi all! There was much talk of MMUs at this year's Meetup (a particularly good one I thought this year!), so I was wondering if someone might take a stab at summarising the different options in a way that even simple people like me could understand. I'm happy to see the interest. The options I can ...

Wow, you weren't kidding. That was hard to read (up to the 1989 articles, but have not waded through them yet.

Is there a handy link to the respective articles and any errata available? I ask because I have a CoCo1/2/Dragon MMU solution that replicates the CC3 MMU config, and running OS9L2 on it is I think the true test of how well it works. Pere's asked to test a unit, but since there's prior art on this, m...

~MS & ~FS are supposed to be connected together on the D64 motherboard. The schematics had a problem whereby the original was creased right where that connection was. On my lower case board, and probably as per the 200E board, ~MS on the 6847 is connected to the socket, whilst ~FS is connected to ~...

On the original lowercase PCB, pin 37 of the header (FS) is not connected to anything. You can see this here: Screenshot 2024-11-20 224806.png This is the original PCB photos superimposed, the bottom reversed, and the top is set to 50% opacity. Pin 37 on the header is the 4th from the right top. Not...

Hi Jim, Sorry - I have been busy on other things. I have conquered the file once, but every time I look at it again it confuses me. I view the file in a hex editor, 256 bytes wide, so that each character can then be read downwards over 12 rows. You then get 2 sets of 128 characters in each 12 rows....

Very nice! It's also good that you managed to reduce the board size. If the eprom could be changed by one in PLCC package and the rest of the components rearranged, maybe we could get two boards in a single 100x100 pcb thus helping reduce the price. Congratulations! Actually, you can now, as one of...