Thanks for the great replies.
I have been giving this lots of thought over the last few days before posting on here.
Excellent point about the clock stretching Jeff as that hadnt occurred to me, So now im wondering if the IO chips need the main clock or can i supply a secondary clock to them ???
So, If i had a7.2mhz crystal and used a ripple counter (hef4040b? good to 20mhz @5v) i could generate the other freqs at the same time as the main clock, i could also set up a jumper to set system speed for testing and too bypass wait states.
I really want to get the most from making the PCB's as i dont want have to remake any (4 week delay :/ ) also i want the most ,bang for buck out of them for future.
As soon as i can get the CPU/RAM/ROM board made i can improvise rest on perf while im designing other boards,
As for Memory map.....
16 or 32k for ROM selectable on jumper
32 or 48k for RAM selectable on jumper
IO page 1 at FC00 thru an ac138 for 8 IO's - 0 or 2 WS (again jumpered)
IO page 2 at FD00 thru an ac138 for 8 IO's - 0 or 1 WS (again jumpered)
Should be plenty for just about anything.
Using a modular design is 3.6mhz even attainable ?? Guess if its on a jumper it should be easy to find out
For storage i am waiting for a ch376 to arrive, (8Bit bus, Fat decoding on board......Nice )
The V9958 may be a bit of a problem as i cant find all info yet but will make a separate video board, Idea is i can use serial through 6850 as a start until i can get video board made.
Going to slightly adjust the basic rom on Grant Searle's webpage to get me up and running while i learn 6502 assembler
Im hoping to get some schematics done over the next few days if possible.
The propellors sound interesting and will have a look into those.
EDIT: ....... WHAT A PILCHARD........ Can see chips use PHI2 and not the input Clock *FACEPALM*