Alright, so I kind of went down a rabbit hole with my testing trying to find a methodology that would be representative. I had originally planned on testing the U12A against the results I had already collected when I got the DRP4 to replace my NH-D14, but I was never really happy with my temps overall (~92-94 C) with the following setup:
Software: Prime95 29.4b8 small FFTs
CPU: 4790K at 4.5ghz all core, 1.23 V which became 1.26 V after LLC offset and everything else on auto
Mobo: Gigabyte Z97 Gaming G1
Ram: 32 GB of G-skill Sniper PC2400
Case: Fractal Design Meshify C with the solid top from a Mini-C to try and directionalize the airflow
Intake: 2x 140mm Noiseblocker E-loops
Exhaust: 1x 120mm fractal design Venturi HP
One thing I noticed was that the package power on the CPU was all over the place, anywhere from 90-165W and I was definitely getting clock throttling, which I wasn't savvy enough to look into when I tested the NH-D14. So I thought since I was tearing down the PC anyway, I would delid the CPU and start over with the U12A and a full suite of NF-A12x25s (3x as intake and 1x as exhaust).
During the delidding process, right away I noticed that the stock paste between the chip and the IHS was rock hard and based on the pattern it left on the chip was already delaminating. After scrapping off all of the adhesive, coating the SMD resisters/caps in liquid electrical tape and applying the conductonaut liquid metal, I decided not to reseal the CPU to minimize the bond line between the CPU and IHS. I put everything back together with the U12A and reran Prime95 29.4b8 small FFTs with the same settings and my temps dropped to 71 C max after 30 minutes. With such a giant disparity, I couldn't exactly use the previous data on the other coolers as it would be like comparing apples and walnuts.
So then I went down the path of looking at standardizing a testing setup that would be robust and relevant to real world conditions. I bumped the vcore to 1.27 knowing that the offset would stick the voltage right at 1.3 and set the boost profile to be 4.7ghz 2-core and 4.6 4-core and tried locking the boost power to 125 W. Unfortunately this boost power is the most finicky value and the number reported by HWMonitor never got to where I'd set it in the bios. For example, to get 125 W on small FFTs, I had to set the boost limit to 145 W, but then this setup was unstable in large FFTs. So then I tried to aim for 150 W (knowing that auto had it going all the way to 165 W) and had to set the boost value to 180 W. This generated more heat at the same clocks and voltage readings, which must mean that the cores are getting fed additional current, and now the memory controller seemed unstable because I'd get a new blue screen in the blend tests.
So, I bumped the RAM voltage from 1.5 to 1.65 manually because the XMP profile which said that it was increasing the voltage to 1.65 in the bios' memory page still had 1.5 in the voltage page and that's what was being reported by gigabytes system viewer. This seemed to fix the stability issues in blend and large FFTs but was increasing the package power to ~158 W at the boost limit of 180. Thus, I dropped the boost limit to 175 and that seemed to limit the package power back to 150 W.
At this point you must be saying to yourself, "Allhope, you're crazy, why are you so focused on the package power?" and thats because I feel like this is going to be the only representative value to compare coolers in a thermodynamically sound way. CPU Temp (heat stored) = heat generated - heat dissipated, and each cooler is going to behave differently enough as it is with their different number of heat pipes, differently sized interface plates, different fin densities, and different total surface area, that I didn't want to go convoluting things further with unstable input loads. (My gods, this feels like my PhD all over again!)
Anyway, long story short, I've gotten to a place that I'm happy with the setup, but I don't have time for any more testing this weekend. As far as the U12A goes in totally qualitative terms: It is a beast of a cooler for its size.
The following summarizes the tests with the cooler:
CPU: 4790K at 4.6ghz all core, 1.27 V which became 1.3 V after LLC offset and boost power set to 175 W for a reported 150W in small FFTs
CPU thermal interfaces: Conductonaut between the chip and the IHS and Cryonaut between the IHS and the CPU cooler.
Mobo: Gigabyte Z97 Gaming G1
Ram: 32 GB of G-skill Sniper PC2400 locked to 1.65 V
Case: Fractal Design Meshify C with the solid top from a Mini-C to try and directionalize the airflow
Intake: 3x 120mm NF-A12x25's locked at 60% fan speed (~1400 RPM +- about 20RPM variance in the PWM) [100% PWM ~ 2200 RPM)
Exhaust: 1x 120mm NF-A12x25's locked at 60% fan speed (1400 RPM) lined up precisely with the fans of the cooler to minimize turbulence.
CPU Cooler: NH-U12A with 2x NF-A12x25's
Ambient Room Temp: 24 C (measured by wall thermostat)
Software: Prime95 29.4b8 (then corroborated with 29.7b1)
After 15 minutes of small FFTs
CPU Cooler Fan Speed - Package Temp
2000 RPM - 76 C (52 C delta)
1800 RPM - 76 C (52 C delta)
1600 RPM - 78 C (54 C delta)
1400 RPM - 80 C (56 C delta)
1200 RPM - 83 C (59 C delta)
1000 RPM - 85 C (61 C delta)
800 RPM - 89 C (64 C delta)
600 RPM - 94 C (70 C delta)
I don't have any sound pressure measuring equipment, but in my current setup pegging everything at 60% (1400 RPM) is an unobtrusive noise level that I barely noitce, so I set a fan curve ranging from 40% (~900 RPM) at idle to 70% (~1600 RPM) if the CPU ever gets to 90 C.
