3D Temperature, Noise, Power Consumption
There is something we’d like to clarify before going into details of 3D operation. If a powerful graphics card holds the GPU temperature at, say, 60 or 80°C, this is almost never the credit of the cooling solution or the graphics card vendor, but the temperature threshold programmed into the cooling profile. Typically, the fan speeding up will create sufficient air flow to tackle GPU heat, and even reference cards are capable of maintaining 60 or 65°C. It's all a matter of fan speed and operating noise. However, each cooler does have its limits.
The programmed GPU temperature threshold of the overclocked card typically is the same or at least similar to the default, which is 80°C in the case of AMD's Radeon HD 5870. In the case of the MSI R5870 Lightning, the threshold is 65°C, and the cooling solution will try to stay below this temperature even if the card is overclocked. Although the temperature threshold should not be seen as a quality item, it is indeed reasonable to drop the temperature threshold if the cooling solution allows, and as long as you don’t increase cooling noise too much.
On the overclocked reference card, the default cooler has to handle the additional heat dissipated by the +50 MHz GPU clock speed. The overclocking has a more noticeable impact on the noise level at +0.5 dB(A) and the temperature increases from 80 to 82°C. The difference is smaller on the factory-overclocked MSI board, which is because of the smaller overclocking margin. The card already runs at 900 MHz, and the additional 25 MHz we could achieve without voltage tweaks are less significant. The cooler with its two fans can easily handle the additional heat caused by our overclocking. Effectively, there is only a little noise difference between the reference card and the optimized overclocking models. The latter offers higher default clock speeds and cools more efficiently, resulting in similar cooling noise as on the reference board.
The power consumption differences between the default clock speeds and the overclocked settings aren’t as significant when looking at peak load conditions. We measured a difference of 10%, and this it typically because of adjusted voltage settings on overclocked graphics cards. This is oftentimes necessary to ensure stable operation.
The last two diagrams show the events during the 13 minute benchmark run. You can see that the graphics processor reaches peak temperature within minutes. Both cooling solutions provide similar results when the benchmark takes a quick break and doesn’t cause GPU load, as the temperature decreases quickly.
The percent value in this diagram has only limited meaning, as it is calculated from the maximum fan speed. The noise level is more relevant. MSI’s Lightning card is a bit better than the reference cooler from AMD. We found the steadiness of the results more impressive, as MSI’s twin-fan cooler is capable of handling sudden temperature differences much quicker than the reference cooler design.
However, you can avoid high noise level or frequent fan speed changes through the Catalyst driver or an overclocking tool, such as MSI’s Afterburner, by simply setting the fan to a fixed speed. Keep in mind that you should look at the GPU temperature if you decide to go this way, as the cooling performance is of course limited by a fixed, low fan speed. There are dynamic fan speed profiles, but we found that this option is sometimes locked, which means that you can typically only choose between the factory auto setting or a fixed fan speed.