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

The SilverStone Permafrost Series AIO Coolers Testing Results, Maximum Fan Speed
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  • drexnx - Wednesday, June 17, 2020 - link

    wish we'd get a teardown of the pumpblock, seems like after many years of asetek stagnation we're finally seeing performance move forward again in AIOs Reply
  • warrenk81 - Wednesday, June 17, 2020 - link

    page 2 typo: "The bottom of the main block assembly reveals a sizable, square cooper block." Reply
  • eastcoast_pete - Wednesday, June 17, 2020 - link

    Maybe my information is outdated, but isn't there a small, but significant difference in the overall shape (slightly concave vs. slightly convex) of AMD's vs. Intel's heat spreaders that can really affect cooling performance? I may have missed it, but are the copper blocks "fitted" to the respective CPU type? If not, some of that cooling potential is likely being wasted.

    Also, with current "enthusiast" kind Intel CPUs reaching over 250 W TDP at peak use, any chance of showing results with a steady 250 or 200 W load?
    Reply
  • PeachNCream - Wednesday, June 17, 2020 - link

    I'm seeing a drop down menu option to select various wattage from 60W up 340W including the 200W and 250W options you would like. Reply
  • eastcoast_pete - Wednesday, June 17, 2020 - link

    Yeah, I should have been clearer; that comment/request was in regard to the last graph, which doesn't have the drop-down selection, and is for 100W only.
    Interestingly, no response by anyone yet on the question about the shape of the copper block; I didn't think it'd matter, until I read some tests that showed a pretty significant difference depending on how true the heatsink matches the heat spreader's shape
    Reply
  • p1esk - Wednesday, June 17, 2020 - link

    "the contact plate is not large enough to cover Ryzen Threadripper processors"

    OK thanks
    Reply
  • Arbie - Wednesday, June 17, 2020 - link

    For those interested, the Noctua NH-D15 is close to the Fractal Design S36 here, except that there's no data on Noctua above 38 dBA:

    https://www.anandtech.com/show/14621/the-noctua-nh...
    Reply
  • Beaver M. - Saturday, June 20, 2020 - link

    And thats with 2 fans.
    Plus you always have the option to sound-insulate your case, which helps a lot on air coolers, while the pumps of AIOs are pretty impossible to get silent due to their vibration.
    Reply
  • edwardav54 - Wednesday, June 17, 2020 - link

    No RGB please. Reply
  • AdditionalPylons - Thursday, June 18, 2020 - link

    If my colleague working with permafrost research would be into stationary PCs I'd buy this for him at once. =)
    That said, I may consider this in a mITX build for myself at some point.
    (I've only had one AIO - an Asetek for LGA775, years ago. Wasn't bothered with the relatively minor pump noise. Have since used Noctua air coolers and been happy with that.)
    Reply

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