14.3.16. BogoMIPS Value too low

Question:

We are only seeing 263.78 bogomips on a MPC5200 running at 396 MHz.
Doesn't this seem way to low ?? With a 603e core I'd expect 1 bogomip per MHz or better.

Answer:

No, the values you see is correct. Please keep in mind that there is a good reason for the name BogoMIPS.

On Power Architecture®, the bogomips calculation is measuring the speed of a dbnz instruction. On some processors like the MPC8xx it takes 2 clocks per dbnz instruction, and you get 1 BogoMIP/MHz. The MPC5200 takes 3 clocks per dbnz in this loop, so you get .67 BogoMIP/MHz.

See also The frequently asked questions about BogoMips.

Question:

But I have a MPC8572 running at 1.5GHz, amd it shows only 150 bogomips. This cannot be correct?

Answer:

This value is indeed correct.
"With recent kernels, when build with ARCH=powerpc, we now use the hardware timebase instead of bogus processor loops for short timings. Thus our bogomips value is no longer the speed at which the processor runs empty loops, but the actual processor timebase value as obtained after calibration at boot. " - Benjamin Herrenschmidt