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Performance difference on single vs multi core

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

  1. phwashington

    phwashington Guest

    I posted this originally on alt.comp.hardware.overclocking.amd

    Since there are a number of people over here that know about CPU's
    they might be able to enlighten me on what is happening here. I'm not
    picking on AMD, I just don't have any Intel's to test it on.

    We are seeing some significant performance differences on single vs
    multi-core processors on AMD chips.

    We have a database application that we are running on XP which also
    does regression analysis.

    I have asked the manufacturer of the software if they have seen this,
    but they have not. They are using Clarion from SoftVelocity to build
    the application.

    on some systems I know the core others I do not

    AMD Athlon Socket 939 (single) 4000+ 102 secs

    AMD Athlon 64 X2 (Toledo) (single) 4800+ 145 secs

    AMD Athlon 64 (Unknown) (dual) 3500+ 184 secs

    AMD Black Edition (Brisbane) (dual) 5000+ 780 secs
    (Overclocked to 3GHz)

    AMD Athlon 64 (Brisbane) (dual) 5200 +

    AMD Quad Phenom 9950 810 secs

    We then installed the application on an operating system installed as
    guest in VMWare

    AMD Quad Phenom 9950 92 secs

    Any idea on what is going on here. This really doesn't make sense. I
    would expect maybe a little performance hit but 5 to 6 times

    The only hint I can see of the issue may be the run made on the
    Toledo. While it's clock speed is faster It's performance is still
    worse than a 4000+. My understanding is that a Toledo is a dual core
    with one core disabled.
    phwashington, Oct 29, 2008
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  2. phwashington

    Paul Guest

    Start by running a pure compute benchmark. SuperPI runs on a single
    core. Select enough digits of PI when running it, so that the
    size of the cache does not influence the results. For example,
    run 1 million digits and 32 million digits.



    AMD processors feature Cool N' Quiet, use a "CPU driver" downloadable
    from the AMD site, and in the hardware, have a programmable
    multiplier. By making multiplier and voltage changes (FID and VID),
    the processor can change from a full power state, to a power saving state,
    up to something like 30 times a second.

    When there are problems, sometimes an application will end up
    "stuttering". For example, Anandtech, in their last series
    of movie playback benchmarks, found a difference in playback
    smoothness, with CNQ enabled and disabled. So they had to
    run benchmarks under both conditions, on the assumption a
    pissed off customer would turn off CNQ, to get the smoothness
    they wanted. This causes a higher average power dissipation
    on the processor (important in the HTPC market).

    I don't know anything about which application is best to monitor
    the processor state. There is an AMD Power Monitor application
    here, and presumably it can tell you the currently used FID and VID.


    Maybe after you've benchmarked with SuperPI, and compare clock speeds
    from the various processors, you'll get a better feeling for where
    to look next. Perhaps there are peripheral differences between
    boxes ? Faster disks ? More memory for an application level cache ?
    And so on.

    I have run into the odd person, who has done everything to set up
    their AMD processor in terms of CNQ, CPU drivers, Microsoft patches
    and the like. And for some reason, the processor stays in "low gear".
    Which is why it would be nice to be able to monitor what speed the
    thing is running at.

    Also, try running your processor hardware descriptions through the
    list here. The "Toledo Single" stops at 4000+.


    AMD has their own list of processors, but surprisingly, choose
    not to list everything they've ever made. (And I'm not referring
    to the one-off lots they ship to OEMs - their server processor
    list is far from complete.)


    Paul, Oct 29, 2008
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  3. phwashington

    phwashington Guest

    Thanks for the reply.
    I'm probably going to re-install the 5000+ chip in the system this
    weekend and give it another whirl. Right now it's running the phenom
    processor with VMWare.
    But I would still like to find out what the issue is.
    phwashington, Oct 30, 2008
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