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The rates the timer can be run at.
Each names what it counts. The hardware divides one of four clocks by a power of two, and these are the ones a program can afford: every overflow runs the handler.
| Hz | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 | 4096 | 8192 | 16384 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| CPU | 0.05% | 0.1% | 0.2% | 0.4% | 0.7% | 1.5% | 2.9% | 5.9% | 12% | 23% | 47% |
The figures are for an original Game Boy. CGB double speed mode halves each of them, since the handler costs the same and the processor issues twice as much in a second.
The hardware counts faster than 16384 Hz, but the handler would take more of the processor than the program has left to give.
Each rate is paired with the fastest clock that reaches it, which leaves
Timer::count dividing the period as finely as it can.