| Bits | Description |
|---|---|
| 7 | 1 if ROMCS is asserted on the expansion bus (read only) |
| 6 | 1 to allow peripherals to override the ULA on some even port reads (rotronics wafadrive) |
| 5 | 1 to disable expansion bus nmi debounce (opus discovery) |
| 4 | 1 to propagate the max cpu clock at all times including when the expansion bus is off |
| 1-0 | max cpu speed when the expansion bus is on (currently fixed at 00 = 3.5MHz) |