More than likely, I will be using 2-3 Propellers for my design. But not explicitly for address decoding or glue logic.
I still think a 65C02 running at 2MHz is a nice machine so I would be more than happy to hit that target. In fact, some other designs I want to build using the *cough* *cough* Z80, would run at a maximum speed of 4 MHz. So, I'm not trying to build anything massive.
After I build a few 8 bit machines, I want to tackle either a 16 bit or maybe 32 bit machine. But by that time, I will be using FPGA (which I'm learning) with maybe a Propeller as the main CPU (or ATMEGA) or maybe even a 68K running as a softcore. Lots to learn and do.
But my first computer is going to be pretty simple. I will more than likely use some discrete logic for memory decoding and 2-3 Propellers for video, audio and I/O.
Also, I've been trying to crunch some numbers. Nothing concrete. But I plan on running the Propellers with a 6.25 MHz crystal which gives you 100 MHz. Four clocks per instruction (minimum) yields 25 MIPS. Or, 40ns per instruction.
65C02 running at 2 MHz is 500ns per cycle....250ns per half cycle. So, in theory, that gives me a maximum of 6 Propeller instructions per half-cycle. With real life being probably 2-4 instructions. So, not much can be done other than clocking a shift register, etc. So, I get it now.
I mean, you would think 100MHz microcontroller could handle a measly 2MHz 6502....
But at least I understand why it can't for many things. Not without devoting several COGS to get parallelism. But like you said, if I were to do that, might as well use discrete logic.
Lessons learned.
Cat; the other white meat.
