|PowerColor AX6990 4GBD5-M4D Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by Bruce Normann|
|Sunday, 20 March 2011|
Page 16 of 19
PowerColor HD 6990 Temperatures
It's hard to know exactly when the first video card got overclocked, and by whom. What we do know is that it's hard to imagine a computer enthusiast or gamer today that doesn't overclock their hardware. Of course, not every video card has the head room. Some products run so hot that they can't suffer any higher temperatures than they generate straight from the factory. This is why we measure the operating temperature of the video card products we test.
To begin testing, I use GPU-Z to measure the temperature at idle as reported by the GPU. Next I use FurMark 1.8.2 to generate maximum thermal load and record GPU temperatures at high-power 3D mode. The ambient room temperature remained stable at 25C throughout testing. I have a ton of airflow into the video card section of my benchmarking case, with a 200mm side fan blowing directly inward, so that helps alleviate any high ambient temps.
I tested the PowerColor Radeon HD6990 4GB GDDR5 video card with both BIOS settings, figuring that a higher clock would have a definite effect on the GPU temperature. I was right, there was a measureable difference, but you'll see that it wasn't a major one. With just the basic Windows Aero desktop running I recorded 41C in idle mode, with a moderate idle fan speed of 27%, as dialed up by the internal fan controller. Both GPU temperatures increased to 77C after 30 minutes of stability testing in full 3D mode, at 1920x1200 resolution, and the maximum MSAA setting of 8X. With the fan set on Automatic, the speed rose to a 45% under full load, which shows how much thermodynamic muscle is required to keep two of these top GPUs under control. I then did a run with manual fan control and 100% fan speed. I was rewarded by a significant increase in fan noise and a matching reduction in load temperature to 60C.
77C is not a particularly low result for temperature stress testing, but considering how much power was coursing through the PCB traces of the board, it's a wonder that it wasn't any higher. I'm used to seeing video card manufacturers keep the fan speeds low, especially with radial blower wheels that make a racket at higher speeds, but AMD had to run it up to nearly half speed to cool off two of their biggest and hottest graphics cores. I was able to knock an impressive 17 degrees off the load temps by running the fan at either 90% or 100%, which is what I recommend for sustained gaming. Heat kills electronic components, and there's no joy in assisted suicide for your video card, but you'll need some decent gaming headphones with closed backs. It's only because I am obsessive about heat that I say this, as the stock settings keep the GPUs within reasonable temperature limits.
I then tested the PowerColor Radeon HD6990 with the overclocking BIOS settings, and there was a measurable effect on the GPU temperature. With Windows Aero desktop running I recorded the same 41C in idle mode, at the same idle fan speed of 27%, because the GPU was still running at the same speed and voltage. The GPUs increased to 81C after 30 minutes of stability testing in full 3D mode, at 1920x1200 resolution, and the maximum MSAA setting of 8X. With the fan set on Automatic, the speed rose to 50% under full load, which is significantly higher than you will ever see with a single-GPU card that has a blower wheel. The run with manual fan control and 100% fan speed brought back the fan noise and reduced the load temperature to 65C. As I said earlier, it's a measurable increase in temps, but nothing to worry about.
Load temps got up to a maximum of 81C when running continuous gaming benchmarks with the most challenging titles, at the lower 830 MHz clocks and automatic fan speeds. This is a few degrees above the stress-test-maximums, so it's pretty obvious that AMD and PowerColor are using some power throttling techniques to keep temperatures in check when using what they have called "Power Virus" tools like FurMark. They've publicly said as much, and I can't blame them, as it's obviously a big balancing act to keep the GPU running at peak performance while staying within the power and temperature envelopes that the modern PC can handle. I still think that FurMark is doing a good job of emulating a real-world graphics load, at least compared with today's DirectX 11 graphics titles. I was able to reduce the hottest games down to 69C with 90% fan speed, so for those of us who aren't afraid to use higher fan speeds and can live with the noise, the stock GPU cooler will easily do the job.
FurMark does do two things extremely well: drive the thermal output of any graphics processor higher than any other application or video game, and it does so with consistency every time. While FurMark is not a true benchmark tool for comparing different video cards, it still works well to compare one product against itself using different drivers or clock speeds, or testing the stability of a GPU, as it raises the temperatures higher than any program. But in the end, it's a rather limited tool.
In our next section, we discuss electrical power consumption and learn how well (or poorly) each video card will impact your utility bill...