==== Instruction timing : currently in r008.5.14 ====
In r008.5.14, in GA, I do use begin of edge for IO_ACK instead of state.
In r008.5.14, M1 reached same time of IO_ACK are ignored (not M1) in WAIT_n generator.
In r008.5.14, MEM_WR has an OSD menu choice to switch between "quick" and "slow", "slow" mode does insert ONE WAIT_n during detection of MEM_WR. This switch exists because somes games are running in "slow" mode and others in "quick" mode.
==== Instruction timing : talk about r008.5.14 ====