New Saturn asm "add loop" benchmark for the HP48G

[Jonathan Busby]

Assuming the cycle counts from "Cycles du Saturn" are accurate ( which I doubt as they don't contain any half or quarter cycles due to Saturn bus NSTR cycle stretching ), then an estimated count for Werner's original non-unrolled add loop would be :

\( \dfrac{3900000 \cdot 60}{49} \approx 4775510 \)

This is 392325 larger than the actual count. Again, assuming the cycle counts I've been referencing are accurate, then this means something is stealing about (392325/60)*49 ~ 320398 cycles/sec . I know TIMER2, when running, steals a small amount of cycles for the purposes of keyboard polling every 1mS. Also, the card detect circuitry steals cycles while it's enabled. I'm dubious as to whether the aforementioned cumulative overhead steals ~320398 cycles/S, but I'm not sure. If the lower performance of my code can't be explained by taking the above into account, then we have a mystery.

Regards,

Jonathan