Ok, plans (everything based off the same 8MHz clock):

First iteration

Create a new cpu_clock() which will do single clock cycles for the cpu.
Each clock will run the glue/mmu/shifter_clock functions that runs from cpu_do_cycle() today
Each clock will run a new version of cpu_step_instr() that does the following:

If cpu->icycle is larger than 0, do nothing, just return; the previous instruction hasn't "finished" yet.
Fetch instruction (or use a previously prefetched one) if the previous instruction has consumed all its cycles
Run the new instruction (which is the exakt same code as today). This instruction will run everything on the first clock cycle, but will report how many cycles there should be in total (cpu->icycle) before the next one is to be run
Handle exceptions if at the appropriate cycle
Decrement cpu->icycle
Return from function

Rewrite movem to work with the above scheme (it does not give a proper cpu->icycle, all other instructions do)

This should take care of the basic bits, and the next code iteration can begin

Second iteration

Rewrite one instruction at a time to be reentrant and be called for every cycle. The instruction should then handle its read/write and the prefetch at the proper cycle points. This will remove the need for a bus_read/write_long() since the words will be read separately. It will not handle waitstates.
Either here or the next iteration, move the new cpu_clock() code into something more of a system clock, and call cpu_clock() from there, just as it'll call mmu/glue/shifter as well.

Third iteration

Make bus_read/write into a split call, by requesting the action and handling the result. This will make it possible for an external part to insert waitstates onto the cpu.

Clocked CPU #105

Description