The Noctua NH-U12A is designed for Intel Socket LGA2066 / 2011 / 1156 / 1155 / 1150 / 775 and all modern AMD processors. Here is an overview of the system and testing methodology
MSI Z390 Ace – Z390 Chipset
Intel Core i9 9900k (3.6Ghz) Octo Core 8 x 256KB L2 Cache 16MB L3 Cache
The CPUID System Monitor was used to obtain and record system temperature data and being that this is a quad core processor we need something that will work across all of the cores at once. For this task we're using a new version of Prime95 (p95v255a) that will allow you to spawn (n) instances to test with.
Editors note: Even though the Windows 10 task manager reported 100% processor usage we could never attain a 100% of the rated heat output as documented by Intel when using Prime95 as a basis for that heat production. Knowing this we ran the stress test until the maximum temperature was attainted and stabilized.
Other things to consider when judging software induced heat output.
a) Clock throttling by the processor at high temperatures.
b) Normal software isn't designed to produce maximum heat output.
c) Variances of cooling temperature.
d) Variances in CPU load.
e) Inaccuracies in thermal diode readouts.
Of course the list goes on..
Our testing methodology is aimed to provide a real world look into this heatsink given the test system provided.
A C/W rating can quickly be calculated using this formula.
C/W = (CPU temp - Ambient temp)/(Variance(%) * CPU Watts)
Allowed variance for this test = 85%
CPU Watts = 95W (or 124W due to turbo clock)
0.26 C/W = (60C - 26C)/(.85(124W))
For this next test the CPU speed was cranked up to 5.2Ghz and the test was re-run.
To calculate a new C/W rating for this test we will need to factor in the increased processor wattage. The formula and constants for this are listed below.
ocC/W = dCPU Watts * (ocMhz / dMhz) * (ocVcore / dVcore)2
ocMhz = 5200
dMhz = 4700 (boost)
ocVcore = 1.4
dVcore = 1.2
The variance still applies for our C/W calculation
Allowed variance for this test = 85%
CPU Watts = 190W
0.27 C/W = (80C – 26C)/(.85(190W))
In our heatsink and waterblock tests we don't really focus on overall load temperatures but rather how well the product can remove heat given a specified heat load. Since this is a real world testing method we need to take into consideration real world variables and estimate tolerances. This is why we normally only apply 85% of the total wattage output to our heat calculations.
The resulting C/W number is used to rate how efficient a heatsink or waterblock is based on the given heat load. These numbers can be used to determine heat capacity, the larger the difference the less efficient the heatsink is. (aka not good for overclocking)
As the charts show we have a heatsink that can clearly handle the Core i9 9900k. The 80c overclocked load temp was a little high for my tastes but the system ran like a dream. During this review I also tested the cooler on a variety of different systems including a Core i9 7900X. This is a 10 core processor and quite the little heat monster with a 140w TDP.
During these tests the 7900X showed a 83c load temperature at 4.3Ghz (the stock “boosted” clock) and 94c under overclocked conditions at 4.4Ghz using the MSI Game Boost dial. I ended up using the 9900k due to the increased range between the factory and overclocked settings as they offered a wider range and more variety. What you can take from this is that even on a 10 core monster, like the 7900X, the Noctua NH-U12A can still keep it cool.
Keep in mind these calculations are provided for demonstration purposes only and may not reflect the actual lab tested C/W rating, but we're pretty close.