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OMAP-L137 Low Linux BogoMIPS

JLD
Prodigy 90 points

Other Parts Discussed in Thread: OMAP-L137

 

The BogoMIPS value is printed during linux boot, or you can type
"dmesg | grep BogoMIPS" at the bash prompt.

I have noticed on other ARM processors running Linux that the BogoMIPS
value is about equal to the CPU clock in MHz. On the L137 it is only
about half of what is expected. i.e. The clock is 300 Mhz, but the BogoMIPS
are only 149.

This would seem to indicate that the L137 has only about half the
processing power of other ARM processors at a given clock rate.

Why is it so low? Is this a problem with the linux port, or a hardware issue?

Thanks.

 

 

  • 0
    TI__Intellectual 1920 points

     

    According to the Data Sheet (http://focus.ti.com/lit/ds/symlink/omap-l137.pdf , pg 67) , the default value for SYSCLK2= SYSCLK1/2.  Therefore, its possible that the PLLDIV2 value needs to be changed to 1.

    EDIT: Actually it is SYSCLK6, so it should be ok.

     

  • 0 in reply to Devin
    Prodigy 90 points

    Devin,

    So then, MAYBE the mv linux kernel is only running at half of what it claims....

    To fix this is probably a 1-line code change . I would be happy to try it.

    Can you point me to a source file & line # in the mv kernel and what I should try?

    Thanks,

    -J

     

  • 0 in reply to JLD
    TI__Intellectual 1920 points

    Hello J,

    I am working on getting more information.

    Devin

  • 0 in reply to Devin
    Expert 1345 points

    From what I can see from the docs, SYSCLK6 is the ARM Subsystem (SYSCLK1/1).

    SYSCLK2 =  ARM RAM, ARM ROM, EDMA, DSP ports, EMIFB (ports to switch /2 SYSCLK1 / 2

    Thus DSP and ARM should be running at 300MHZ.

    Kev

     

     

  • 0 in reply to Kevin Halloran
    TI__Mastermind 24340 points

    That is true.

    JLD, bogomips are not always = to the CPU clock rate.

    For some processors it can be 1/2. Like described in this article: http://en.wikipedia.org/wiki/BogoMips

    Please remember that BogoMIPS are not the best comparison benchmarks at all...

  • 0 in reply to Mariana
    TI__Mastermind 41665 points

    Mariana is right on, the BogoMIPS factor for an ARM9 processor is .5 * CPU frequency, so if you see a BogoMIPS at boot of ~150 that means you are running at ~300MHz. For example on another device, I have a DM355 board that boots up with 108 BogoMIPS, and the processor is actually running at 216MHz.

    Bernie's Terminal Log said:

    root@xxx.xxx.xxx.xxx:~# cat /proc/cpuinfo
    Processor       : ARM926EJ-S rev 5 (v5l)
    BogoMIPS        : 107.72
    Features        : swp half thumb fastmult edsp java
    CPU implementer : 0x41
    CPU architecture: 5TEJ
    CPU variant     : 0x0
    CPU part        : 0x926
    CPU revision    : 5
    Cache type      : write-back
    Cache clean     : cp15 c7 ops
    Cache lockdown  : format C
    Cache format    : Harvard
    I size          : 16384
    I assoc         : 4
    I line length   : 32
    I sets          : 128
    D size          : 8192
    D assoc         : 4
    D line length   : 32
    D sets          : 64

    Hardware        : DaVinci DM355 EVM
    Revision        : 3500000
    Serial          : 0000000000000000

     

    This being said if you got a BogoMIPS of 300 on the OMAP-L137 it would mean either your BogoMIPS measurement is broken or your processor is being overclocked by 2x.

  • 0 in reply to Bernie Thompson TI
    Prodigy 90 points

    Thanks  all for clearing this up.