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Testing processor performance

Discussion in 'AMD Overclocking' started by phwashington, Sep 29, 2008.

  1. phwashington

    phwashington Guest

    I have been trying to test cpu performance using Nbench and have found
    that I get better results running XP on VMWare system using a quad
    core than I do on an XP system running a dual core AM2 5200+ or
    5000+ . I clocked the same system with the two different processors
    and was only able to obtain results about half of what I was able to
    achieve on an XP system running in VMWare on top of a quad core 9850
    linus system. For measurement I was most interested in Floating point
    and Integer MOPs/sec.
    I originally saw the problem when running a database program and found
    out it was five times slower on the system running on system A running
    directly on dual core vs system B running in VMware on a quad core
    9850. The VMware system has only one CPU allocated to it.
    When I realized I had a problem, I suspected first the hard drive,
    then the MB, then the CPU. All have been changed out, along with the
    Any ideas on why I am seeing this difference? I just feel like there
    is something I am not understanding here. I don't really want to
    install a quad core into a system when it is only utilizing one CPU
    phwashington, Sep 29, 2008
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  2. phwashington

    Paul Guest

    The Phenom has a different cache structure. It has a shared L3. The
    dual does not. The memory subsystem is also different. I believe the
    Phenom has the ability to run the two channels independently (and is
    probably configured that way by default), whereas the dual core would
    have them linked together.

    If the clock rates were identical, it would suggest your benchmarks
    or activities have a high dependence on cache and memory.

    Try disabling Cool N' Quiet, forcing both processor to run at full
    clock speed all the time.

    This thread was a discussion of the things needed to properly install
    WinXP on AMD. With SP3 out, I expect "Update 4" is already taken care
    of. Leaving the "CPU driver" ? Start reading the thread from back to
    front, to get the latest scoop.


    (Last post)

    Processor drivers are available here, for the various processor types.


    Paul, Sep 29, 2008
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  3. phwashington

    Paul Guest

    I should get my terminology right.


    Ganged versus unganged.

    "The second peculiarity of the integrated memory controller
    is the fact that it is implemented as two independent 64-bit
    controllers rather than a single 128-bit interface. This
    allows the memory of Phenom platforms to work in two
    modes: ganged and unganged. The first one is analogous to
    the usual 128-bit dual-channel mode. The second one implies
    that the CPU can deal with two independent 64-bit memory controllers
    thus processing two memory requests simultaneously, which is good
    for multi-threaded environments."

    Linkage, refers to the relationship between core and memory clocks

    "Phenom memory controller is also interesting because it runs at
    a different frequency than the CPU clock: it uses its own clock
    frequency multiplier and runs at 2GHz on all currently available
    CPU models. They did it this way to ensure that the actual memory
    frequency always matches the desired one, which was not always the
    case with previous generation AMD processors. They frequency was
    obtained by applying integer dividers to the CPU clock speed value.
    So, the Phenom memory controller may set the DDR2 SDRAM frequency
    at exactly 400, 533, 667, 800 or 1066MHz at any clock speeds."

    Paul, Sep 29, 2008
  4. phwashington

    phwashington Guest

    Thanks for the info. This is a heck of a lot farther than I got.
    This is pretty freakin dizzying.
    I'm not going to complain about AMD not having a web site where they
    could be the information in concise format. Where there customers
    could find it and apply to there rigs. I mean there are so many
    operating systems that are running on AMD dual core and AMD Phenom
    processors that it would be impossible for them to find one that might
    cover 90%+ of the user base.

    I forgot in my original post that one of the users was running the
    same program on an AMD 3800+ chip in 1/5th the time mine was running,
    so this is becoming a little frustrating.

    I don't know if it is possible, but could it be throttling down the
    CPU some how. Because when I run the program in VMware I see the CPU
    usage go up to 85-95%. When I run it on the other system, I only see
    10% max usage. Running though the same problem. On one system it
    takes 12 minutes and on the other it takes 1.5 minutes.
    phwashington, Sep 29, 2008
  5. phwashington

    Paul Guest

    If you disable Cool N' Quiet, the machine should operate at the rated
    clock speed. (Check the BIOS.)

    You can also try the power monitor application, and see what it reports.
    Another program would be CPUZ, but I don't know how it handles the
    dynamic nature of Cool N' Quiet.


    Paul, Sep 30, 2008
  6. phwashington

    phwashington Guest

    Thanks for your help.
    I finally got my integer and floating point Mops/sec up, but the
    program I was trying to run still operated slowly.

    So for anyone that may see this yes you need the lates AMD Drivers to
    get the best performance even with SP3.

    Everything else worked fine, I was really impressed with the
    responsiveness of the system. But whenever I tested the integer and
    floating point operations I got really low numbers, until I installed
    the AMD Drivers.

    But for this system I am going to give up for now and get a Quad Core
    and run XP in VMWare. The performance matches the values my cohort
    was getting on an
    3800+ and I'm really spent to much time on this.

    Thanks again Paul.
    phwashington, Sep 30, 2008
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