ATI RADEON 3850/3870 (RV670)

320 Shader Processors and 256-bit Memory Bus

Now about the cooling systems. Let's examine a custom cooler from TUL as well as reference coolers installed in products from HIS/Sapphire.

PowerColor RADEON HD 3850 Extreme 512MB PCI-E
TUL engineers equipped the card with 512 MB of memory and raised operating frequencies using a special cooler from Zerotherm It's a round cup, consisting of many fins threaded on heat pipes. Everything is made of copper. There is a big fan in the middle of the cup. Unfortunately, while similar coolers from Zalman are noiseless AND highly efficient, this cooler misses one component - noiseless operation. This device rustles a little. It's not loud, but it's present. That's a problem, but it's not big. Cooling efficiency is high. Note that memory chips are not cooled.
ATI RADEON HD 3850 256MB PCI-E
It's a usual design - a narrow closed heat sink with a fan at one end that blows the air through. The core touches the heat sink through a copper plate. Memory chips are also cooled with thermal gaskets. The default fan speed is very low, 10-15% tops. So there is no noise. We'll find out whether such low fan speed is really necessary.
ATI RADEON HD 3870 512MB PCI-E
It's a two-slot device, if we can say so. That is a card with this cooler will take two slots in a system unit. The cooler is based on a large closed heat sink. The air is driven through the heat sink and then thrown out of a system unit through the grid in a bracket. The cooler is also noiseless, because it works at low speed.

As the new version of RivaTuner (written by A. Nikolaychuk AKA Unwinder) already supports RADEON HD 3xxx, let's have a look at monitoring results.

ATI RADEON HD 3850, default cooler settings

As we have already mentioned, the default fan speed is very low, but the core gets very hot. We've heard that the first 3850 cards were set to higher fan speed (28-30%), and the core temperature did not exceed 70°C. PLEASE NOTE! RivaTuner ALLOWS to adjust fan speed on cards of the reference design. So you are recommended to set fan speed to 30-40% manually. The cooler will remain quiet, but the core temperature will drop to 60°C.

PowerColor RADEON HD 3850, default cooler settings

This card is equipped with a special cooler. It's a bit noisy, but its speed cannot be adjusted. The core is cooled very effectively.

ATI RADEON HD 3870, default cooler settings

This situation is similar to what the reference 3850 demonstrates. The cooler is very slow, but the temperature is quite high. AMD engineers apparently tried too hard to make the cooler noiseless, and forgot about the temperature.

ATI RADEON HD 3870, 70% fan speed

Look what happens if the fan speed is set to 70%, that's the upper threshold beyond which the cooler becomes noisy. The temperature is paltry for this kind of cards!

ATI RADEON HD 3870, overclocked to 825/2400

Overclocking results.

Bottom line: you can safely set the fan speed to 40-50%, the cooler will still be quiet, but the core temperature will drop.