With GPUs becoming ever larger and more power-hungry even the mighty DirectCU II would eventually be out-matched. Not, it must be said, in terms of absolute cooling potential but rather the unacceptable noise level reaching this potential would necessitate. Something had to give, and that has come in the form of the DirectCU III, the first major upgrade to the DirectCU lineup.
In releasing the DirectCU III ASUS improve upon previous models in two core aspects - fan design and heatpipes.
Heatpipe Design
Heatpipes are inherently bi-directional in that vapour travels away from the source of the heat whilst condensed liquid is drawn back to the source. Aiding in this dynamic, especially the speed at which liquid is drawn back to the hotter areas of the pipe (i.e. zones directly above the GPU), boosts the efficiency of the cooler such that it can handle ever higher TDPs.
The rate at which liquid travels within a heatpipe is dictated by the compostion of the heatpipe's internal surface. There are two major approaches:
- Sintered Power Heatpipe - which is excellent in promoting capillary action but tends to impede liquid when it would flow more naturally.
- Grooved Heatpipe - which doesn't impede flow back, but has low capillarity and hence gravity is more of an impediment.
A DirectCU heatpipe however utilises a combination of sintered powder and grooves to provide the best of both worlds. For similar 6mm-diameter heatpipes a DirectCU pipe outperforms these types by ~25% and 50% respectively. But that's not all.
DirectCU III is the first GPU manufacture to utilises two 10mm diameter heatpipes (or 'superpipe' if you will), alongside the more common 8mm and 6mm pipes. These superpipes are two of the three directly above the GPU, and hence have a direct bearing on the efficiency of the cooler. The addition of 10mm DirectCU pipes greatly increases the rated TDP of DirectCU III, making it more suitable for large high-TDP GPUs such as AMD's R9 Fury. However, that's only one half of the equation.
Wing-Blade 0dB Fan Technology
In addition to modifications to the heatpipe design ASUS also re-engineered their fan, as well as adding a third to the overall cooler design. The result is their patented Wing-blade 0dB fan technology.
Conventional fans blades introduce eddy currents at the very tip as the fan rotates, reduing overall air pressure and flow. Taking inspiration from the US Airforce's A10 Warthog Attack Jet, ASUS created Wing-Blade 0dB Fan Technology. The design places a small downward stop at the tip of the blade, disrupting this current and thus increasing air pressure; ASUS have measured the effect as improving overall pressure by 105% at these edge zones, no mean feat.
ASUS's Wing-Blade 0dB Fans are also straighter and wider than comparative models. These larger blades give rise to a 25% larger blade area overall, which improves air flow by ~4%. Similarly larger fans also reduce the gap between each blade (in this case by a whopping 37%) which increases air pressure by 4%. Pretty respectable.
Cherry On Top - Strix Armor Protection
The final component to the R9 FURY’s cooling isn't strictly part of the DirectCU III formula, but nonetheless is a much-need cooling and aesthetic feature: Strix Armor Protection. Strix Armor Protection is, in essence, a solid GPU backplate which serves a dual-role.
The first, and most important, is to reinforce the regidity of the card and provide greater protection to the GPU socket. The heavy nature of the DirectCU III solution would normally place the card and GPU socket under a lot of stress, not least due to requiring firm and consistent contact with the GPU. The STRIX Armor not only increases the card rigidity, but also provides anchor points for the cooler so weight is more evenly distributed across the PCB. In the long term this should improve reliability, whether kept long-term in a chassis or continually swapped with other GPUs on a test-bench.
The second (and somewhat less vital) purpose of the Strix Armor is to act as an attractive heatspreader for the underside components such as memory chips, components which don't typically benefit from active cooling. The card also includes a STRIX LED on the top-most edge of the cooling shroud, adding just a little more to the overall premium look and feel to this GPU.
Although the DirectCU III cooling on this GPU does include an exhaust port outside the rear of the chassis much of the heat dissipated will still linger, requiring suitable chassis air-flow to exhaust it out the rear and top of the case. That is unfortunately one of the consequences of high-end cooling within a dual-slot form factor - dissipating heat from the GPU takes priority over expelling it from the chassis.
It's likely that the DirectCU III will be limited to the flagship AMD and NVIDIA GPUs for some time to come, and may even be broadly unnecessary in its most elaborate incarnation when the industry transitions to 14/16nm. It is however an excellent tool for ASUS to have in their toolbox, and many of the improvements may follow-through into dual-fan DirectCU coolers in the future.
With the DC3 cooler detached from the graphics card we can see take a look at the inner-workings and see the full extent of that monolithic PCB. ASUS has placed a brace support running from the IO plate across the top to supply even more protection to prevent the board from bending.
At the very heart of DC3 OC is the R9 Fury GPU aka Fiji. This GPU comprises of 3584 (56 Compute Units) created by the 28nm process. The highlight with AMD’s new Fiji-based GPUs is the introduction of HBM which introduces the 4096-bit memory interface. AMD are able to significantly condense the layout and form factor in this region.
Our graphics card employs a 12+2 phase Super Alloy Power II design, along with Super Alloy II CAPs and chokes too. The end result means better temperatures, longer lifespan and less noise. The construction of this card is built 100% by machine via ASUS Auto-Extreme. Stringent quality control techniques are used and production is executed with absolute precision.
