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AM335x BogMIPS

Steve Tsai
Intellectual 380 points

As I know AM335x uses Cortex A8 core, so it has 2 DMIPS/MHz performance. When I set the CPU clock to 800Mhz, I will get about 800M BogoMips in Linux. Should it be 1600M BogoMIPS? I know am335x has only 16bits memory bus. Does the memory bus cause the lower performance? 

Steve

  • 0
    TI__Guru**** 393215 points
    Hi Steve,
     
    A frequently quoted definition of the term BogoMips is "the number of million times per second a processor can do absolutely nothing". So what you see is OK, at 800MHz this is the proper value.
  • 0
    Genius 3685 points

    Linux Bogomips is calculated by executing a simple loop:

    - count down a register

    - jump back if register > 0

    For ARM Cortex A8, you need 2 Instructions for each loop iteration. You will get 800.000.000 loop iterations == 1.600.000.000 Instructions/second.

    The bogomips loop is executed from L1 cache, so the memory interface has nothing to do with the bogomips number.

  • 0 in reply to Wolfgang Muees1
    Intellectual 380 points

    I know kernel estimates BogoMIPS roughly and it is not so accurate. The BogoMIPS is around 1400 on omap4 running at 700MHz and the performance of cortex A9 is 2.5 DMIPS.  Does it mean that the omap4 has double performace than AM335x per core and Mhz?