Also used by Aleste 520EX CPC clone:
  F4X0h Aleste_PPIPortA_PsgPortAAleste PPI Port A, Baudrate Timer 0 (RX Clock)                (W)  F4X1h Aleste_PPIPortA_PsgPortAAleste PPI Port A, Baudrate Timer 1 (TX Clock)                (W)  F4X2h Aleste_PPIPortA_PsgPortAAleste PPI Port A, Baudrate Timer 2 (FUTURE)                    (W)  F4X3h Aleste_PPIPortA_PsgPortAAleste PPI Port A, Timer 0-2 Control Registers                (W)
  Clock Input for RX/TX is 4MHz, Clock output goes to a 8251 chip,
  Clock Input for FUTURE is HSYNC, Clock output selects 1st/2nd color set,