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

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

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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On this page we present some super high resolution images of the product taken with the 24.5MP Nikon D3X camera and 24-70mm ED lens. These will take much longer to open due to the dimensions, especially on slower connections. If you use these pictures on another site or publication, please credit Kitguru.net as the owner/source. You can right click and ‘save as’ to your computer to view later.

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We installed the modified HD6990 into our test bed. An Intel Core i7 990x system, which is CPU watercooled and running at 4.8ghz.

Test System:
Processor: Intel Core i7 990x @ 4.8ghz.
Cooler: Danger Den Watercooling.
Motherboard: Asus Rampage III Black Edition.
Memory: 12GB GSKILL 2133mhz Memory.
Power Supply: Corsair AX1200W.
Hard Drives: Patriot Pyro 120GB & 2TB Samsung hard drive.
Optical Drive: Asus BluRay drive.
Graphics: Sapphire HD6990 with reference cooler and Arctic Cooling Accelero Twin Turbo 6990 (modified with Xigmatek XAF F1451 & F1452 fans).



We are testing today at the higher bios setting of 880mhz. Remember that the cards won’t be covered under warranty at this setting (if you modified the HD6990 like we have it hardly matters anymore anyway!).

Room ambient was maintained at 24c throughout testing to ensure accurate results.





With the two Xigmatek XAF fans in place, idle temperatures dropped even further, from 40c with reference cooler, to 34 c with the Arctic cooler & fans to finally 30c with the XAF 140mm fans in place.





The modified Accelero Twin Turbo 6990 cooler drops the idle temps by a further 4c, and by 3c when gaming. Furmark load temperatures are unchanged – hitting 71c.



The reference card takes basically 2 minutes to return to idle, so we run out of graphing space to fully highlight how inefficient the cooler really is.

As we documented in our review earlier this week, the Accelero Twin Turbo 6990 reduces this time to 26 seconds … a good indication of the design improvements incorporated by Arctic Cooling.
When we replace the 120mm fans with the 140mm Xigmatek units, this time is reduced by a further 5 seconds. A total time of 21 seconds is very impressive.

Time to test the noise levels.

We have built a system inside a Lian Li chassis with no case fans and have used a fanless cooler on our CPU. We are using a heatpipe based passive power supply and an Intel SSD to keep noise levels to a minimum. The motherboard is also passively cooled. This gives us a build with completely passive cooling and it means we can measure noise of just the graphics card inside the system when we run looped 3dMark tests. Ambient noise in the room is around 20-25dBa. We measure from a distance of around 1 meter from the chassis and 4 foot from the ground to mirror a real world situation.

Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on only the video card. It also brings us slightly closer to industry standards, such as DIN 45635.

We also load the card with FurMark.

KitGuru noise guide
10dBA - Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA - High Quality Computer fan
40dBA - A Bubbling Brook, or a Refridgerator
50dBA - Normal Conversation
60dBA - Laughter
70dBA - Vacuum Cleaner or Hairdryer
80dBA - City Traffic or a Garbage Disposal
90dBA - Motorcycle or Lawnmower
100dBA - MP3 player at maximum output
110dBA - Orchestra
120dBA - Front row rock concert/Jet Engine
130dBA - Threshold of Pain
140dBA - Military Jet takeoff/Gunshot (close range)



28 dBa is the accurate limit of our testing equipment so we can’t give the true readings for the Xigmatek 140mm XAF fans. The Wave Blade technology certainly is impressive as can be seen from the results above.

In the real world, the card is basically inaudible, and you would need to have your ear very close to the video card to even hear that it was on, and running – even under full load.

To put this into perspective, this HD6990 is running quieter than many of the modified HD6790′s and HD 6850′s we have tested in recent months. When factoring in the performance and subsequent heat output this is incredible.

[siopao1984]

AMD’s HD6990 is a powerhouse of a graphics card. Sadly the AMD development team felt that using a tiny, high spinning fan was a good idea, and the product has been marred with irritating noise emissions since it launched. Until AMD step up their game with a good ‘reference’ cooling system, it comes down to third party companies to fix the situation.

The Arctic Cooling Accelero Twin Turbo 6990 has rectified the problem and should sell well between now and the New Year. It may cost $150, but if you can afford the HD6990 in the first place then there is a good possibility that this won’t bother you too much.

Since our ‘world first’ review of the Accelero Twin Turbo 6990 earlier this week our readers have been asking me if it was possible to improve the product even further. While I could have opted for a performance Delta Fan cooled solution to drop temperatures even further, we would be back at square one with high noise emissions.

I decided to use two of the Xigmatek XAF F1451/F1452 fans which cost around £15 each in the United Kingdom. I wasn’t sure initially if the Accelero cooler could house such large fans normally used for chassis cooling, but as testing has shown it is possible to mount two 140mm fans without a problem. If we spent time we could create something more substantial (and more attractive) for the mounting system. That said, for the purposes of this article, it held in place just fine.

With this modified cooler, the HD6990 was idling at 30c, only 6c above room temperature and when gaming it was registering 58c … much better than the 84c+ from the reference cooler.

While we like the Arctic Cooling 120mm fans, there is certainly further room for improvement if you are willing to make a little effort in changing the fans and creating a custom mounting system. We lowered noise emissions to the limits of our testing equipment while improving the performance.

We love this modified HD6990, it is not only faster than any other graphics card in our labs, but it is now quieter.