. For MB: isChipSelected[0] = true. So do this on Reset() or for Phasor when switching to MB mode.
. Add "Notes on Phasor's AY-3-8913 chip-select & r/w"
. Refactor some common code into SY6522::UpdatePortAForHiZ()
Mockingboard or Phasor cards can be inserted into any slot.
Change Config->Sound to that slots 4+5 to be individually selected for the 3 soundcard types.
Add MockingboardCardManager class to manage multiple cards and mix the sound buffers.