Because of timescale pressures, the data separator design in the ASIC has been deleted rather than improved . Thus all models with a disk drive use an external SED9420 data separator.
===Reading of write-only I/O registers===
The following has been tested:
When the following I/O ranges are read 7fxx, bcxx, bdxx, efxx and dfxx (these are write-only I/O registers), the last byte of the I/O read instruction is put onto the bus and read. e.g. if IN A,(C) is used to read from one of these ports, the last byte of that instruction is read back.
There is no hardware that is driving these registers, so the data is effectively "floating".
===Reading of unmapped ASIC register RAM===
When a read of an unmapped address is done from the ASIC register page (this is where there is no readable register here, or no register has been assigned), the last byte of the instruction used to do the read is return. e.g. if LD A,(&5000) is done, the last byte of this instruction is then read.
There is no hardware that is driving these registers, so the data is effectively "floating".
===Power requirements===