Radeon HD 6850 & 6870 CrossfireX review

Graphics card cooler performance examined

Let's have a look at the temperatures the reference based custom cooler offers.

We now fire off a hefty shader application at the GPU and start monitoring temperature behavior as it would be when you are gaming intensely and continuously, we literally stress the GPUs 100% here, as you can see in the graph.

Below an overview of peak / maximum measured temperatures in comparison with other cards. These temperatures with your average game will typically be lower.

At IDLE one or two cards in CrossfireX (case closed) will all have a 40-45 Degrees C temperature on average. Once we setup Crossfire and add more cards we see very different behavior.

We note down the highest temperature of hottest GPUs. We note down the hottest running GPU temperature we measured and for the 6850 the cooling is worse, temps reach 88 Degrees C, which is a little too high for my taste.

The 6870 has better ventilation and cooling as it seems, and did not push over 76 Degrees C, which is fine. All remain under control, though make sure you have plenty airflow inside your system to ventilate hot air.

Noise Levels coming from the graphics card

When graphics cards produce a lot of heat, usually that heat needs to be transported away from the hot core as fast as possible. Often you'll see massive active fan solutions that can indeed get rid of the heat, yet all the fans these days make the PC a noisy son of a gun. I'm doing a little try out today with noise monitoring, so basically the test we do is extremely subjective. We bought a certified dBA meter and will start measuring how many dBA originate from the PC. Why is this subjective you ask? Well, there is always noise in the background, from the streets, from the HD, PSU fan etc etc, so this is by a mile or two an imprecise measurement. You could only achieve objective measurement in a sound test chamber.

The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBA level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement. Frequencies below 1kHz and above 6kHz are attenuated, whereas frequencies between 1kHz and 6kHz are amplified by the A weighting.

There's a lot of differences in measurements amongst websites. Some even place the DBa meter 10cm away from the card. Considering that's not where you ear is located, we do it our way.

For each dBA test we close the PC/chassis and move the dBA gun 75 cm away from the PC. Roughly the same proximity you'll have a PC in a real-world situation.

When you start to accumulate graphics card in one system then the DBa levels tend to much higher as the dynamics change, all related to thermals of course.

• 6850 - In IDLE with two cards we measure roughly 39 DBa (=silent) while reaching 45 DBa (well above PC noise) when full stressed.
• 6870 - In IDLE with two cards we measure roughly 39 DBa (=silent) while reaching 42 DBa (well above PC noise) when full stressed.

Though the R6850 in CrossfireX mode is much more noisy, it was not at an irritating level. It was just airflow that you are hearing, not squeaky or high pitched tones. So it's very doable.

The R6870 really impresses cooling wise, with two cards massively stressed the noise levels remain at the level of a normal PC, that was really good to see, well hear ..