BigEd wrote:
Same for page 1, I think. Not quite such a boost, but I think it would help.
Actually, a local memory with dual byte access for page 1 would be a major improvement for one of the strengths of 6502: interrupt response time. Currently an interrupt would cost you the time to store 3 bytes on stack before a jump through the vector. With local memory that is reduced to zero.
Return from interrupt still costs you the retrieval of the same 3 bytes. Local memory can reduce that to perhaps a single cycle.
Same for JSR and RTS you can save a lot of cycles. PHA and PLA would also save a bit.
I think this is quite a big win at the modest cost of local memory and probably not that much added logic. Best of all it should be rather transparent to the programmer. The dual port local memory could perhaps be used both for ZP and page 1.