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 Post subject: Determination of the Heat Dissipated by an 8800 GTX
 Post Posted: July 16th, 2007, 4:49 pm 
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Joined: January 20th, 2007, 10:16 pm
Posts: 873
Location: Long Beach, CA
  • Introduction

    We recently published an article focusing on the actual core temperature of Intel's Kentsfield processor. In this document, we first measured the actual heat dissipated by Kentsfield into the cooling device in order to estimate the Junction to Case Thermal Resistance. Today, we are posting the results of our heat dissipation tests on an 8800 GTX. But, without a designated thermal tool for GPU we have no real interest for the Junction to Case Thermal Resistance. Knowing the actual heat dissipated in the GPU cooler is nonetheless interesting in particular to estimate the total amount of heat dissipated by a liquid cooling loop.

    Now, one of the positive aspects of this study is that we were able to separately measure the heat load generated by the GPU and that of the memory and I/O chip modules. What we did to accomplish this was to repeat the testing methodology outlined in the above article and changing the testing water-block by either a dedicated GPU water-block or a full coverage block.

    Limitations:
    We intentionnaly limited our tests to stock voltage since only the most extreme users perform the delicate operations required to increase the 8800 operating voltage.

    Methodology:
    As we did in “Estimation of the Junction Temperature on Kentsfield” we just implemented our radiator testing methodology to an 8800 GTX. The graphics card is liquid cooled with first a MCW60 and then a Stealth water-block. Inlet and outlet lines temperatures are measured with RTD. Flow rate is maintained to 0.5 GPM and measured. The coolant inlet temperature is kept constant to 25C.

    We measured the heat load while the graphics card was loaded with different applications. We used Rivatuner to set/monitor clocks and to monitor the GPU temperatures. The GPU voltage was measured directly on the PCB. We won’t be able to publish Heat Load Vs. Supplied Voltage since we used only the stock voltage for this study.

  • Results

    8800 GTX GPU only - heat loads under different applications
    Here are the heat loads we measured with the 8800 GTX out of the box under different applications. For information, the card we used is a regular 8800 GTX from Evga. GPU clock is 576 MHz and memory clock is 900 MHz. Under load the GPU voltage drops to 1.27 V.

    Image

    Note:
    Idling in windows dissipates about 50% of a 3D application.


    8800 GTX GPU + Memory + I/O Chip - heat loads under different applications:
    Then, we replaced the MCW60 by the Stealth in order to measure the heat dissipated by the whole card (GPU, memory and I/O Chip).

    Image

    Note:
    Memory and I/O chips represent around 20% of the total heat dissipated by the card.

    Overclocked 8800 GTX GPU head load:
    We compared the GPU heat load when stock to overclocked. We did not change the voltage.

    Image

    Note:
    The heat dissipated by the GPU should be linear with the GPU clock. The additional 72 MHz increased the heat load by 6 W. We can “guestimate” an increase of the heat dissipated by ~0.1 W per additional MHz.
  • Conclusions

    These measurements show the actual amount of heat going from a stock 8800 GTX graphics card into the cooling device. Obviously the heat load will be higher when a volt mod is done.


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 Post subject: Re: Determination of the Heat Dissipated by an 8800 GTX
 Post Posted: August 23rd, 2017, 2:47 am 
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Joined: August 23rd, 2017, 2:31 am
Posts: 0
Location: United Kingdom
Interesting article. The GTX 800 is truly a tremendous machine. I remember that when it came it was expensive a little bit but now it quite affordable.


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