Hi!
WOW! JUST WOW!
That is one cool SBC! You made an ST-506/ST-412 MFM interface? I wouldn't even consider it as it is WAY over my head. I am impressed!
Did the system have on board video? I see it uses the WD FDC2793. Sweet FDC but it sure is a shame practically every recent PC uses the not so nice NEC765 and derivatives.
I'd like to ask about the 68K but I can see that is probably quite a story. Are you familiar with the ECB bus? There was some interest in making 68K home brew systems for ECB. I have seen bits and pieces around but they are pretty rare these days. I am so swamped right now I cannot even consider the possibilities until I get some of these projects finished.
There are two N8VEM ECB peripherals in work right now that could definitely use your help. The N8VEM SBC and ECB backplanes are both done and working so it is too late for those.
The PCBs are available for home brew hobbyists but I would like to transition the project into the peripheral development phase. It's easier said than done though. I am trying to recruit some talented individuals and you just joined the short list.
I am making an ECB bus monitor and am almost done. The schematic and PCB layout is in final review now but I could use some rigorous peer review as to whether this thing will actually work and if there are any improvements I could roll in -- preferrably while preserving the original intent of the design. The original design is derived from a German ECB project in C'T Projekt magazine and follows it fairly well but I have made some extensions and modernized it. The peripheral operates somewhat like a Jade Bus Probe but for ECB bus rather than S-100. It's sole purpose is for hardware/software development but could be used for other Z80 type projects since ECB is so similar to the Z80 bus structure. Here is a link -- caution 29MB download!
http://www.hd64180-ecb.de/assets/download2008/ct_bus_monitor.pdf
The other peripheral is the "crown jewel" of the project at least in my mind. It is the Disk IO board which contains an IDE and an FDC interface. The IDE interface is known working and I have a CP/M CBIOS which supports it. I have my prototype version running in my basement workshop and I am fairly confident it is OK. Here is a link from the N8VEM website. You can barely see the circuit due to all the wiring and it is a relatively low complexity board.
http://n8vem.googlegroups.com/web/IMG_6757.JPG
The FDC section is another story though; my original prototype started getting flaky last year due to poor grounding, I think. I switched the project to all manufactured PCBs to address the poor grounding of the prototype boards and improve reliability. So far, that has paid off nicely and the SBC and ECB backplanes do not exhibit the constant flakiness the original prototypes did. Even my prototype peripherals just work better. However, I halted the project after building the FDC but never tested it. I have some simple FDC software written but again never even tried it out. :-(
Now I am too busy scrambling to get this ECB bus monitor finished and managing the N8VEM project to work on the FDC. My plan is to finish the ECB bus monitor and then start on the testing of the FDC portion of the Disk IO board. Once I know it works and/or rolled in the fixes then I'll convert it to manufactured PCBs like the rest of the project.
So, are you interested in reviewing a couple of designs? The ECB bus monitor is straight TTL chip logic and the pieces are not all that complex. Still the overall function is rather complex due to its use of one-shots, etc. The FDC section on the Disk IO board could use some TLC as well. How are you at building prototypes?
Please consider joining us on the N8VEM project. Seriously, I could use your help. Thanks!
Have a nice day!
Andrew Lynch
http://groups.google.com/group/n8vem?hl=en