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    GPU downclocked when overclocking CPU

    Discussion in 'Alienware M15x' started by Hel20eS, May 11, 2012.

  1. Hel20eS

    Hel20eS Notebook Evangelist

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    When I increase my CPU to 24x throughout, the GPU gets downclocked to 2d (400/900) when playing BF3. Reverted back to stock and the game runs fine as usual. What did I miss?

    I didn't overclock the GPU, just CPU.
     
    Hel20eS, May 11, 2012
    #1
  2. svl7

    svl7 T|I

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    I've explained this issue a couple of times, the power supply of the GPU is somehow badly designed. The CPU can draw as much power as it wants, but by doing this the gpu voltage supply gets unstable and can't deliver enough juice under load.
    You can easily see tho during the combined 3dM11 test - when the CPU is pushed to a certain level, the resulting fps drops severely because the gpu changes it's power state.
     
    svl7, May 11, 2012
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  3. Hel20eS

    Hel20eS Notebook Evangelist

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    My bad for not searching throughly, I was kind of frustrated and wanted a quick answer. So the solution of this is to limit the amount of powerdraw from the CPU?
     
    Hel20eS, May 11, 2012
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  4. svl7

    svl7 T|I

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    Yes, exactly.
     
    svl7, May 11, 2012
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  5. Hel20eS

    Hel20eS Notebook Evangelist

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    sorry to sound noob again but how can I do this?
     
    Hel20eS, May 11, 2012
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  6. DR650SE

    DR650SE The Whiskey Barracuda

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    By not overclocking the CPU ;)
     
    DR650SE, May 11, 2012
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  7. Hel20eS

    Hel20eS Notebook Evangelist

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    then what's the point of 920 lol. but yeah of course that's one of the ways
     
    Hel20eS, May 11, 2012
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  8. The Revelator

    The Revelator Notebook Prophet

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    You can also experiment with TDP. A 920xm will ordinarily require 80-85W to support 24x under full load (test yours with Throttlestop). Try reducing to 70W to see whether throttling/power starvation continues and then adjust until you find the sweet spot that allows max practical CPU o/c without robbing the GPU's performance potential.
     
    The Revelator, May 11, 2012
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  9. Hel20eS

    Hel20eS Notebook Evangelist

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    i'm currently using 72 for both, lower than this and the multiplier becomes unstable when using TS bench.
     
    Hel20eS, May 11, 2012
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  10. The Revelator

    The Revelator Notebook Prophet

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    Well then, if you can't use TDP to arbitrate power between the CPU and GPU, the only course is to follow DR650SE's advice -- don't overclock the 920xm.
     
    The Revelator, May 11, 2012
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  11. Hel20eS

    Hel20eS Notebook Evangelist

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    last question, does undervolted GPU have anything to do with this issue?
     
    Hel20eS, May 11, 2012
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  12. The Revelator

    The Revelator Notebook Prophet

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    Sure, but it's a matter of degree and will vary between cards. An undervolted GPU will generally draw less power, leaving that much more available for the CPU, but at the cost of reduced GPU overclocking headroom. You have to experiment to determine whether and to what extent undervolting the GPU can lead to higher overall performance.
     
    The Revelator, May 11, 2012
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  13. Hel20eS

    Hel20eS Notebook Evangelist

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    ah, so actually it suppose to perform better since I have my GPU undervolted for quite some time. back to stock CPU then i guess :(
    thanks for all the clearups.
     
    Hel20eS, May 11, 2012
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  14. King of Interns

    King of Interns Simply a laptop enthusiast

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    Does this throttling problem exist with the 7970M?
     
    King of Interns, May 12, 2012
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  15. lthuiyi

    lthuiyi Notebook Enthusiast

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    Yes, definitely...
     
    lthuiyi, May 14, 2012
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  16. lthuiyi

    lthuiyi Notebook Enthusiast

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    Hi bro, i find u r using PSU of 240w for M15x?!
    how can u achieve this?
    I mean, only change the power adapter from 150w to 240w won't make any difference in power consumption as the BIOS limit, right?
     
    lthuiyi, May 14, 2012
    #16