|XFX Radeon R7770 Black Edition Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by David Ramsey|
|Wednesday, 15 February 2012|
Page 15 of 17
VGA Power Consumption
Like AMD's Tahiti GPU, the Cape Verde is fabricated on a 28nm process. There are two advantages to making transistors smaller: you can make 'em faster, and they use less power. Both are true here, but AMD didn't stop there, since their Graphics Core Next architecture has a number of clever power-saving features.
Like a modern CPU, a Cape Verde GPU will aggressively clock itself down when its full capabilities aren't needed, reducing current draw with what AMD calls "PowerTune". But they go even further, with "ZeroCore" technology turning off entire sections of the chip when they aren't in use. This features work amazingly well.
To measure isolated video card power consumption, Benchmark Reviews uses the Kill-A-Watt EZ (model P4460) power meter made by P3 International. A baseline test is taken without a video card installed inside our test computer system, which is allowed to boot into Windows 7 and rest idle at the login screen before power consumption is recorded. Once the baseline reading has been taken, the graphics card is installed and the system is again booted into Windows and left idle at the login screen. Our final loaded power consumption reading is taken with the video card running a stress test using FurMark. Below is a chart with the isolated video card power consumption (not system total) displayed in Watts for each specified test product:
* Results are accurate to within +/- 5W.
It's obvious that AMD's power-saving technologies work incredibly well. The card uses almost no power when your system's simply sitting there in Windows; in fact, the power use is so low in these cases that it's hard to discern among the "noise" (power usage will fluctuate by several watts even in an "idling" system).
XFX R7770 Super OC Overclocking
XFX calls this card a "Super Overclock" edition. AMD's standard clocks for the graphics cores and memory of a 7770 GPU are 1,000MHz and 1125MHz, respectively; XFX pushes these to 1,120MHz and 1,300MHz as shown in the GPU-Z screenshot below. Note: Although GPU-Z doesn't check the "OpenCL" box in the "Computing" section, the card does in fact support it.
This is a pretty aggressive overclock, and I found out just how aggressive it was when I tried to push it further. Even increasing the maximum power limits by 20%, I wasn't able to get the card to complete benchmark runs at a mere 1150MHz. That means I couldn't increase the GPU core frequency by 2.68 percent. There's virtually no overclocking room left in this card.