AMD 1090T X6 Phenom II BE
2x2Gb Crucial Ballistix Tracer DDR3-1600
128Gb Crucial C300 RealSSD
Icy Dock 2.5" Adapter
1Tb WD Caviar Black
1Tb Hitachi Deskstar
LG 8x BD-RE 16x DVD-RW
ASUS EAH5870 V2 1G
OCZ Fatal1ty 750w
Cooler Master HAF 932 AMD Edition
AMD installations require removing the stock retention bracket, and mounting the curved bars as shown above. Spring-loaded screws are already attached to the brackets on the base of the C14, so all that is left to do is position the heatsink over the socket and tighten them onto the posts. The included tool allows this to be done with both fans already attached, although seeing where the screw head is to line up the tool through the blades of both fans and the cutout in the heatsink fins can be a challenge. It's probably still easier than installing the bare heatsink and trying to clip on the fans afterward.
Leaving the processor at stock settings of 3.2Ghz @ 1.3V with an AMD Cool'n'Quiet reduction to 800Mhz @ 1.2V at idle, we first try the NH-C14 with the included LNA and ULNA adapters. Using either speed reducer allows the fans to operate virtually silent, with no discernible noise audible from outside the case. OCCT CPU test was used to generate a full load across all six processor cores. Considering that the temp, as registered by the motherboard, is barely above ambient at idle and only in the low 40°s at load, the Noctua is performing quite impressively. The motherboard temp was used in place of the CPU core temp as the AMD offset is unknown.
Using the fans full speed results in a few degrees improvement with the same stock settings, but once the processor is overclocked and voltage increased the NH-C14 can no longer keep the CPU from overheating and eventually locking up. The fans are still reasonably quiet even at maximum velocity, so switching to some noisier but higher flow fans may have different results. However given that the load temp started in the mid 40°s, increased at an initial rate of only 1-2°/min, then five or six minutes into the test began skyrocketing, I believe what we're seeing here is thermal runaway.
Heatpipes are tuned to work within a certain temperature range. If they can't shed heat quickly enough and the temperature gets above their operating range, their phase change properties no longer work correctly. Since there's no direct contact between the fins and the base, the heatpipes are the only method of moving that heat, and once they stop working that's it.
Let's wrap things up with some final thoughts and conclusion.