CPU Speed Register
From SpecNext official Wiki
| Number | $07 |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Sets accelerated clock speed, reads actual speed. |
Read:
| Bit | Function |
|---|---|
| 7-6 | Reserved |
| 5-4 | Current actual CPU speed |
| 3-2 | Reserved |
| 1-0 | Programmed CPU speed |
Write:
| Bit | Function |
|---|---|
| 7-2 | Reserved, must be 0 |
| 1-0 | Set CPU speed (soft reset = %00)
%00 = 3.5MHz %01 = 7MHz %10 = 14MHz %11 = 28MHz (reserved for future, currently gets dropped to %10 14MHz) |
The CPU throttling from 14MHz to 7MHz is not happening in core 3.0+ any more (but if any configuration would require it, or 28MHz mode will be implemented with throttling, it can be seen by reading bits 5-4).