| Bits | Description |
|---|
| 0 | port fffd,bffd ay |
| 1 | port 0f,1f,4f,5f dac soundrive mode 1 |
| 2 | port f1,f3,f9,fb dac soundrive mode 2 |
| 3 | port 3f,5f dac stereo profi covox |
| 4 | port 0f,4f dac stereo covox |
| 5 | port fb dac mono pentagon/atm (sd mode 2 off) |
| 6 | port b3 dac mono gs covox |
| 7 | port df dac mono specdrum, port 1f kempston alias |
Notes:
The internal port decoding enables always apply.
When the expansion bus is on, the expansion port decoding enables are logically ANDed with the internal enables.
A zero bit indicates the internal device is disabled. If the expansion bus is on, this allows io cycles for
disabled ports to propagate to the expansion bus, otherwise corresponding io cycles to the expansion bus are filtered.