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AMD’s flagship HD6990: is silent air cooling possible?

When AMD released the HD6990 it claimed the ‘fastest video card’ title and has held it since March this year. While we love the product we absolutely loathe the reference cooler – AMD’s choice of tiny red fan has been a bone of contention for me now for years and it doesn’t seem to be changing anytime soon. Thankfully Arctic have a firm grasp of the enthusiast sector and released the Accelero Twin Turbo 6990 – an expensive, but class leading cooling solution for AMD’s flagship. Since our review went live a few days ago we have been inundated with emails asking if it would be possible to improve, or swap out the twin 120mm fans for something better.

Arctic Cooling are using good quality 120mm fans (1100D), made in Switzerland. These are built into a plastic shroud specially for the Accelero Twin Turbo 6990 Cooler. If you missed the review be sure to check it out before reading further into this article.

Removing these fans is straightforward, but you need to be careful. We recommend using a flat head screwdriver to prise the plastic clips from the aluminum fins underneath taking care not to snap them. When each side of the shroud pops up, pull them away from the fins. Repeat for both fans. Disconnect the single cable from the HD6990 PCB. Store this in a safe place.

The Accelero Twin Turbo 6990 cooler is a great product – it combines decent levels of airflow, with low noise emissions. Our review highlighted that it dropped temperatures by around 20c, while reducing noise from a maximum of 48.5 dBa to 33.4 dBa.

That 33.4 dBa rating is when both of the 120mm fans are spinning at 100% (or 1,500 rpm each). This is significantly lower than the tiny reference fan solution …. but it still isn’t silent. At a distance from a few feet, even within a closed case, the fans can be heard.

What we are aiming for today is to achieve similar temperature results, but to lower the noise even further, to around 30 dBa (or less) when under full load. Several months ago we wouldn’t have considered this to be possible, but by using the Arctic Cooling Accelero Twin Turbo 6990 we hope to achieve this goal today.

Performance freaks may be disappointed, after all by adding a few 120mm Delta fans it may be possible to lower the temperature by another 10c. To us however this defeats the purpose of the Accelero Twin Turbo 6990 cooler – we want lower temperatures, but it is also important that we reduce the noise levels even further.

Behind the scenes we tried around 5 sets of 120mm fans but weren’t happy with any of them. A few fans created more noise, while reducing the temperatures by a few Celsius while others were silent, but temperatures rose to 80c+ again. Arctic Cooling clearly did their research and opted for two quality fans with a balanced air flow/noise dynamic.

It was clear we needed to think ‘bigger’. I mean literally, bigger.

Could the Accelero Twin Turbo 6990 cope with two 140mm fans? The basic idea sounds good – bigger fans produce greater airflow, while spinning slower. Obviously it isn’t quite as straighforward as just ‘slotting in a few larger fans’, because the quality of the motor and internal design is still massively important.

We were recently sent two of the new Xigmatek XAF F1451/F1452 fans. These are copper bushing axis fans. According to Xigmatek – “Copper bushing axis can guarantee exceptional running smoothness and provide excellent long-term stability.”

These fans are using an Aeronautical Oil System Bearing and push 90.3 cfm of air each, while being rated at less than 18dBa. They do ship with a 4 pin header, but also have a 4 pin to molex adapter in each box, making them ideal for a variety of systems. Just be aware that if you use the 4 pin headers to ensure that the motherboard won’t consider them chassis fans, effectively slowing them down when you least want it.

Xigmatek rate the RPM from 800 to 1,300 rpm with a 150,000 hour life span, which is already slower than the 120mm fans that Arctic Cooling supply with the Accelero Twin Turbo 6990 cooler. With the extra 2cm on each blade and the quality internal design could we mount these without a problem?

We used a combination of thick cable ties and wire to mount the 140mm fans to each side of the cooler. We ensured that the bigger fans didn’t protrude too far down and block the fitting of the card at the PCIe slot. Looking directly down it was easy to align the outer shell in place.

Each of these fans is supplied with a molex adapter which will prove useful with motherboards which don’t have spare headers. The only downside is the untidy mess they make. We stuck a plastic grip to the top of the outside fan, tidying up the cabling a little. Obviously our fan mounting system could be cleaner, but each of the 140mm fans was held in place perfectly, without any movement.

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  • Colm

    Very very nice indeed, great idea ! the card would end up costing more than my system but what the hell.

    £560 for card, £100 for cooler and £30 for fans.

  • Uriel

    It should be possible to create bracket system to fit under the cooler and underneath the heatpipes. would be a ton of effort however. Shame arctic didnt make the shroud system detachable, rather than make it part of the fans.

  • John

    [quote]Several months ago we would have considered this to be impossible, but by using the Arctic Cooling Accelero Twin Turbo 6990 we hope to achieve this goal today.[/quote]

    I think you meant ” we wouldn’t have considered this to be possible”.

    Good read, i’m glad you actually did this and you also proved this cooler can be modified. Actually i’m surprised how good the initial fans were. Good job!

  • Colm ODonnell

    Great idea and very interesting. I love to read about cooling and constantly try to improve my systems with better fans and other tweaks.

    Its cool to see that the cooler can take 140mm fans, as there are tons of options out there for modifying.

  • Dan

    Very nice indeed. good idea, but it would scare me.

  • OmegaRED

    I love the fact that you even did this though I think looking at those Gaming DB differences I could settle for 29.5. I expect my speakers or headset will drown that out easily.

  • JamesM

    Anyone know if you can get the AC cooler anywhere in the UK or even Europe (apart from auction website cia US)?

  • Hi JamesM, a lot of people have been asking this, sadly it seems very hard to find. ill have a chat with Arctic Cooling this week.

  • JamesM

    @Zaron, would be really grateful. thanks!

  • JoshK

    Hey Zardon, great write-up! I actually ended up getting the exact setup since I was impressed by the numbers you had. Runs quite and cool, couldn’t be happier. This is the only real article covering this cooler but was as informative as I needed.

    One question for you, when I installed the card in my case [600t], the card is drooping from all of the weight on the far end. I’m trying to come up with a way to compensate and get support on that end but am having trouble coming up with a solution that isn’t ghetto-rigged. Any ideas [assuming you ran into same issue]?

  • Josh, you actually make a very good point. After the mod, the card is very heavy and it does put quite a strain on the slot, even screwed into the case. I can’t think of many ‘official’ ways of supporting the card on the far side as you say, although I did notice that HIS bundle a ‘weight lifter’ product with their HD6950 ICEQ card which you can see here http://www.kitguru.net/components/graphic-cards/zardon/his-radeon-hd-6950-iceq-x-plus-edition-review/2/

    Not sure if you can buy these separately, but it would help.