NZXT Kraken G10 Graphics Adapter

Cooling | Graphics Cards
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The most critical aspect of heatsink installation is firm, even contact between the base and the die for efficient heat conduction. Ideally it should also be a simple procedure with the user having to handle as few pieces of hardware as possible. We chose the NZXT Kraken X41 to try on the G10. This cooler was substantally better than the X31, due to its large radiator and its 140mm fan. The HIS HD 5870 iCooler V Turbo we used for GPU cooler testing in the past was hauled out yet again. We measured an estimated 215W DC power draw from this card at full power load, which is in the ballpark for current high power single GPU cards.

The 215W
HIS HD 5870 iCooler V Turbo was hauled out yet again

The bare GPU on this card is somewhat protected by a ridged perimeter, which looks like a raised frame, and limits the amount of angled or askew pressure that can be applied to the die while the heatblock is being screwed down. Those of us who recall the days of bare CPUs, before the advent of heatspreaders, know that such askew pressure was the chief cause of many accidental CPU deaths.

Lining up the mounting holes to the bolts.


My earlier comments about the relatively lightweight quality of the G10 bracket were borne out during installation. The metal around the pump is thin and flexible enough that it begins bending almost as soon as you start tightening the knurled nut that fits atop the threaded bolt. It bent slightly on the other side as well, but not nearly as much as there is much more metal, and thus less flex. This was disconcerting, to say the least, and the feeling of lack of control was exacerbated by the fact that there are no unambiguous mechanical cues on when the screws are tight enough. Unlike the best bolt-through heatsink retention mechanisms, the G10's 4-bolt mounting does not have "preset" maximum tighteness points or preloaded captive springs that screw down to a certain point and no further. I suspect these bolts are threaded far enough that it may be possible to overtighten to the point where the die could crack, especially if the four nuts are not evenly tightened. The foam pad on the backplate adds to the risk factor as well, because it can compress unevenly, and allow askew pressure on the GPU.

The G10 bracket is highlighted to show the bend on the left side.

I proceeded very slowly, eyeballing the mating between the pump and GPU often to ensure they remained as parallel as possible while turning the nuts systematically and incrementally. There is no way to know for sure whether the pressure is even across the GPU surface. All you can do is hope it is even, tight enough, but not too tight. Worst case scenario: If you overtighten, you might damage the GPU; if you don't tighten enough, the contact might not be good enough and your GPU could burn as soon as it powers up.

To be fair, other tech sites have reviewed the G10, and none have reported a GPU mishap. Still, I am not convinced that such mishaps cannot happen, and I believe the mounting system could be made far more foolproof. The desire for a more robust and foolproof mounting system is not unreasonable, considering that the G10 could be used with video cards that cost many hundreds of dollars.

Kraken X41 mounted on the HIS HD 5870 card via the G10, lying atop the side panel of a Fractal Design Define R3.

A Fractal Design Define R3 stripped of 3.5" drive cages to make more room has been our graphics card and cooler test platform case for a couple of years. It is not ideal for housing large watercooling radiators. While the radiator of the X41 is not that big, it's quite wide, and therein lies the problem. The Define R3 is equipped with 120mm vents and fans; they are too small to comfortably fit the X41 radiator.

A choice had to be made: Find a way to make the X41 radiator fit in the R3 for this test, or upgrade to a new larger case. The latter option would make all of our previous test data not directly comparable to future test data; the former would be a PITA and be a somewhat compromised installation for the G10/X41. It was a tossup, and in the end, the R3 was retained for this last test.


Before the test could proceed, however, another obstacle loomed: The HIS HD 5870 iCooler V Turbo video card refused to produce a picture on our monitors. I tried two different monitors, with DVI, HDMI and old VGA connectors. I also tried installing the card on a different system. I tried, finally, with the original stock cooler. The card remained resolutely dead.

When the GPU was examined, there was no apparent evidence of physical damage; the die was not chipped. It's not clear why the HD 5870 card died. It has been handled around the lab for four years; it may have lasted longer than we could reasonably expect, given the amount of handling reference test gear is subject to.

So back to the drawing board.

A known card was needed, one already tested thoroughly by SPCR, with thermal, acoustic and power qualities well documented. Ideally it would be a high power card, like the 215W HIS. The closest thing still on hand was the ASUS GeForce GTX 680 DirectCU II OC, a top-end card going back two generations with a measured maximum power of 203W.

Considering the bent frame of the G10, I decided to start fresh with a new, second sample. During installation to the GTX 680, this sample bent in exactly the same wasy as the first. The bending was no fluke. Installation was complete successfully, but this was known only when the monitor flickered on with the boot up info. Whew!

G10 going on the ASUS GTX 680.

Kraken G10/X41-equipped ASUS GTX 680 installed in the test system. The CPU cooler had to be rotated in order for the X41 radiator and fan to fit on the top vents. It was an extremely tight fit due to limited space between the top panel and the top edge of the motherboard. The RAM sticks on the board prevented the radiator from being centered on the vents, so it ended up being secured only with two screws. As explained earlier in the text, this was a compromise installation.

Only two screws held up the radiator, but wedging a bit of foam on the other side prevented vibrations. The vent is smaller than the radiator; the dividing strip in the middle imposes further airflow impedance.

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