Testing Methodology

Although the testing of a cooler appears to be a simple task, that could not be much further from the truth. Proper thermal testing cannot be performed with a cooler mounted on a single chip, for multiple reasons. Some of these reasons include the instability of the thermal load and the inability to fully control and or monitor it, as well as the inaccuracy of the chip-integrated sensors. It is also impossible to compare results taken on different chips, let alone entirely different systems, which is a great problem when testing computer coolers, as the hardware changes every several months. Finally, testing a cooler on a typical system prevents the tester from assessing the most vital characteristic of a cooler, its absolute thermal resistance.

The absolute thermal resistance defines the absolute performance of a heatsink by indicating the temperature rise per unit of power, in our case in degrees Celsius per Watt (°C/W). In layman's terms, if the thermal resistance of a heatsink is known, the user can assess the highest possible temperature rise of a chip over ambient by simply multiplying the maximum thermal design power (TDP) rating of the chip with it. Extracting the absolute thermal resistance of a cooler however is no simple task, as the load has to be perfectly even, steady and variable, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it would be possible to assess the thermal resistance of a cooler while it is mounted on a working chip, it would not suffice, as a large change of the thermal load can yield much different results.

Appropriate thermal testing requires the creation of a proper testing station and the use of laboratory-grade equipment. Therefore, we created a thermal testing platform with a fully controllable thermal energy source that may be used to test any kind of cooler, regardless of its design and or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60 W and 340 W, in 2 W increments (and it never throttles). Furthermore, monitoring and logging of the testing process via software minimizes the possibility of human errors during testing. A multifunction data acquisition module (DAQ) is responsible for the automatic or the manual control of the testing equipment, the acquisition of the ambient and the in-core temperatures via PT100 sensors, the logging of the test results and the mathematical extraction of performance figures.

Finally, as noise measurements are a bit tricky, their measurement is being performed manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being recorded via a laser tachometer. The fans (and pumps, when applicable) are being powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1 meter away from the cooler, in a straight line ahead from its fan engine. At this point we should also note that the Decibel scale is logarithmic, which means that roughly every 3 dB(A) the sound pressure doubles. Therefore, the difference of sound pressure between 30 dB(A) and 60 dB(A) is not "twice as much" but nearly a thousand times greater. The table below should help you cross-reference our test results with real-life situations.

The noise floor of our recording equipment is 30.2-30.4 dB(A), which represents a medium-sized room without any active noise sources. All of our acoustic testing takes place during night hours, minimizing the possibility of external disruptions.

<35dB(A) Virtually inaudible
35-38dB(A) Very quiet (whisper-slight humming)
38-40dB(A) Quiet (relatively comfortable - humming)
40-44dB(A) Normal (humming noise, above comfortable for a large % of users)
44-47dB(A)* Loud* (strong aerodynamic noise)
47-50dB(A) Very loud (strong whining noise)
50-54dB(A) Extremely loud (painfully distracting for the vast majority of users)
>54dB(A) Intolerable for home/office use, special applications only.

*noise levels above this are not suggested for daily use

Introduction & the Cooler Testing Results
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  • jordanclock - Wednesday, August 25, 2021 - link

    I've always wondered why CPU cooler reviews don't include stock coolers. Reply
  • Ian Cutress - Wednesday, August 25, 2021 - link

    https://www.anandtech.com/show/10500/stock-cooler-... Reply
  • jordanclock - Wednesday, August 25, 2021 - link

    It would be nice to have at least a couple of those in this reviews graphs, but jumping between them shows that pretty much every cooler in this review performs much better than a stock cooler, and the worst cooler here is slightly better than the AMD Wraith cooler. I'm guessing the Wraith Prism would be a bit better than that for cooling but everything I found elsewhere suggests that the Prism is not much of an improvement over the (regular?) Wraith. Reply
  • sonny73n - Thursday, August 26, 2021 - link

    I spent extra $10 for that stupid over-hyped Wraith Spire. After 2 days putting up with its poor heat dissipation I got the NH-U12S Chromemax Black. Cost me $70 but it's well worth.

    Does anyone want the useless Wraith? I'm giving it away or it'll go to the trash soon.
    Reply
  • Sivar - Thursday, August 26, 2021 - link

    I used a Wraith while I waited my NH-D15 socket adapter to arrive.
    It performed pretty well. The Noctua only gave me a few degrees C.
    One difference is that I used aftermarket head sink paste. Perhaps stock paste or overly thick paste is the issue?
    Reply
  • MDD1963 - Sunday, August 29, 2021 - link

    If an NH-D15 only netted a loss of a few degrees C , you must have had one hot running and/or overvolted CPU...(some 5000 series Ryzens run a tad warm, to be sure, although this seems semi-normal) Reply
  • Spunjji - Friday, August 27, 2021 - link

    Any extra context on that? Which CPU were you using it with, was it stock paste, and was it the noise that bothered you or the temperatures? Reply
  • sonny73n - Saturday, August 28, 2021 - link

    I've never used stock pastes. It took me more than 15 minutes to clean it off. I've tried both Arctic Silver 5 and MX-4 but they didn't help much with the stock cooler on my non-overclocked 3600x. The NH-U12S took about 10C down with MX-4 paste and it's quieter on high speed.

    Wraith Spire
    Prime 95 max at 84C. Gaming max at 76C.

    NH-U12S
    Prime95 max at 77C. Gaming max at 65C.
    Reply
  • Tams80 - Saturday, August 28, 2021 - link

    Something sounds wrong there.

    But anyway, you paid an extra $60. Of course you got a better cooler.
    Reply
  • AntonErtl - Thursday, August 26, 2021 - link

    We use the Wraith Prism with a 3900X, and it performs surprisingly well. The board apparently does not power-limit the CPU, and putting load in the CPU resulted in 190W above idle power, which the Prism managed to cool. We have temperature-limited the CPU to 70C, now power is only 135W over idle after some time. Cooling this much to such a low temperature is impressive; elsewhere I always read about high temps on the 7nm Ryzens. But the Prism makes a lot of noise for this performance, so I would not use it for a deskside machine. Reply

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