I'm new to the forum and wanted to say hello and introduce my little project. Mike, thank you for bringing me in!
As a young lad I learned programming 6502 (or to be more specific 6510 in C=64), but I never made it to the hardware level (or better: producing too much magic smoke
). Back there a CBM 610 mainboard got in my hands. The board is disassembled and gone, but the parts still remain. I always wanted to build a little system from them, but never came to it. Now eventually it put it on a messy breadboard:ATMega32 for accessing the memory from the PC.
CPU 6509A - not sure if still works, at least on port pin might be damaged.
2xSRAM 2kx8 (one mapped at 0000-3ffff, the other one at c000-cfff)
glue logic (LS139 - Garth, I read your excellent primer, but the only I/O I have so far are two 6525 TPIs behaving like SRAM, so I will have to gate phi2 in for them too).
clock circuit to generate the non-overlapping clock (might run at 2Mhz, but that might cause ringing, so for now I generate a 62kHz PWM, that seems to work).
Amazingly the computer works.
Not amazingly, it shows some quirks. (At first my test memory writes produced a very odd result - two address lines from AVR were swapped; now I am able to write to the lower memory, but the writes to the higher one disappear - the memory locations written to by the CPU contain random data - I hope I will find a solution for that. But reads from there by CPU work fine.)
So much for now - I'm glad that I have not produced magic smoke so far.
Ralf
Do you volunteer to buy it? 
