Port 000  -  8237A-5 Channel 0 Address register

        All PCs except PCjr: Used for refresh by read of one byte in
        every 15 microsecond, then automatically reinitialized to do
        it all again, over and over. See port 083. Write expect start
        address offset LSB, then MSB. Write automatically sets current
        address. Read returns current address offset LSB, then MSB. The
        base address cannot be obtained from this register.