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We're using the AMD-based platform primarily because it offers the flexibility to test an integrated graphics processor with both dual- and quad-core CPUs. The integrated graphics allows us to establish baseline power consumption without an add-on graphics card. The platform is also quite popular in the mainstream segment, so it's well-suited for testing mainstream graphics cards like the Radeon HD 5670 and HD 5770. It is system-limited with the Radeon HD 5870, as you will see.
We left the power-saving features on the Phenom II X4 955 BE and Athlon II X2 250 enabled in the BIOS, and we set Windows’ power policy to Balanced. To lower the base system power consumption even more, we altered Cool'n'Quiet with K10Stat, allowing our processors to run at even lower voltages. Using these settings, our test platform base power consumption hovered around 55 watts at idle and 80 watts during H.264 video playback. This is just right around the threshold where our platform's PSU efficiency drops off.
Our altered voltages mean that this isn’t a default setup, per se. So, these results are not directly comparable if you’re running stock voltage settings. You can see the differences in system power consumption between running with default voltages and our undervolted settings below.
|Idle||Crysis||Adobe Photoshop CS 4||Cinebench R11.5|
We saw slightly higher power consumption figures with the add-on graphics cards at idle. Originally, we guessed that the results were just leakage variations (the differences are between 5 to 10 W). However, given further testing, it became clearer that this wasn’t the case. Running at default voltages gives us idle power consumption scores close or similar to each card’s specifications.
The reason for the higher power consumption is active power use by additional components. You can't really shut off all power to a discrete graphics card, so there will always be some power drain there. Since it employs a lot more circuitry, the drain is larger than the simpler integrated graphics solution. There’s also PSU efficiency to consider. The power levels we’re seeing at idle are around 10% of the PSU’s maximum output.
For PowerDVD tests, the Athlon II X2 250 offers much lower power consumption, so it makes sense to use this processor instead, since it excels in an HTPC environment.
For reference purposes (and just for kicks), we also recorded GPU utilization data for most of the benchmarks used with GPU-Z on a Radeon HD 4670.