* The selected register (port 4) is set to 0 and port read and write increment is not inhibited.
* If reset is held using the "software reset" then reading or writing to the VRAM data port P#0 will cause the CPC to hang. I believe the V9990 is continuously asserting /WAIT to the Z80 but I can't confirm through code.
* Reset will stop any commands in progress and will clear pending interrupts.