Friday, November 28, 2014

Cooling multi GPU configs [THEORETICAL]

Many Crossfire R9 290X and R9 290 owners bought the refrence blower cooler because "it gets better temps in crossfire". This is completely wrong. The refrence R9 290X hits 93C on the uber fan profile when on it's own. So if you put a another heat source bellow it it will hit 95C and have serious issues staying cool regardless of the fact that said heatsource is not dumping the majority of it's heat in the case because the R9 290X above it only has a 2C margin for warmer intake air.
The back of an R9 290/R9 290X gets stupid hot especially the VRM section which is also closest to the intake fan of the card above it. This results in the following happening:
With non reference coolers that dump the used air back into the case this is not an issue because the cards is operating around the 75C range when alone. This gives the non reference card a +20C allowance on intake air before it hits the same temp as the reference design.
Non refrence coolers also have about 2 to 4 times more air passing through their finstacks making the output air of a custom cooler rather cool typically in the 30-40C range depending on load and clocks. Now assuming your case has fresh air going to all areas at all times the 40C exhaust will be mixed with the cool outside air meaning that the top card will at worst be getting air in the 35C range meaning it will hit the 90s. This would look something like the image bellow:
Now I would like to remind you that this is purely theoretical and based on information from around the internet and my experience with my windforce cards. However if anyone is willing to ship me a pair of R9 290X reference coolers I have all the equipment to do full testing of this. If you can ship me a pair of R9 290/R9 290 reference coolers just leave a comment.

Another thing to note is that this only truly applies to really high power draw cards because the blower coolers do in fact keep in case temps lower than radial fan designs just this difference is not big enough to keep 93C cards from hitting 95+C.

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