Dynatron R27 And R24 Versus Noctua NH-U9DX i4

Today we look at three Narrow ILM CPU coolers for Intel's LGA2011 (v3): Dynatron’s mid-sized R27, Noctua’s NH-UD9X i4 and the ASRock-supplied Dynatron R24.


While this isn’t a server-oriented article, only server and workstation techs are probably familiar with the problem we first faced when testing ASRock’s tiny X99E-ITX/ac. Intel designed its Narrow ILM cooler bracket to conserve space in dual-socket boards, and very few enthusiasts brands care about those. Fortunately, Noctua saw an opportunity where few enthusiast brands tread.

A primary supplier of CPU coolers for the server and workstation markets, Dynatron comes into this comparison from the opposite direction. Newegg shoppers are likely to have seen the name while browsing for other coolers, but ASRock brought retail recognition by including Dynatron's low-profile (2U-server) R24 with its X99E-ITX/ac motherboard. The next model up, the 3U-sized R27 is the largest cooler that the firm sells for Intel’s Narrow ILM.

Technical Specifications

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Few Narrow ILM coolers exist, and even fewer are large enough to suit the needs of a desktop Haswell-E processor. Among those few options, these three are the only models that we could find to fit the X99E-ITX/ac in a proper front-to-back orientation. Noctua also offers its single 120mm-fan NH-U12DX i4 for Narrow ILM, but that model must be turned sideways in order to fit the X99E-ITX/ac. The motherboard’s power cable header and CPU socket location make the 120mm cooler a problematic pairing for most cases, but more on that later.

Dynatron R24 And R27

The R24 and R27 offer two different heights of the same fin design - where more fins offer more cooling, and fewer fins provide a lower profile. At 2.7” and 4.3” tall, the R24 and R27 are designed to fit 2U and 3U server enclosures, respectively.

Four heat pipes are flattened on the bottom and machined smooth for direct contact with the CPU’s heat spreader.

The factory-applied thermal compound will be replaced with Arctic MX4 in today’s test.

Also note that the R27 has 0.3” more clearance between the main heat sink body and base. This extra space accommodates the wider 80mm fan being placed above mounting screws where the R24’s 60mm fan sits between.

Densely packed heatsink fans require extra air pressure to ensure adequate airflow, necessitating thick 60x28mm and 80x38mm fans. Both also use heavy-duty motors, which grumble at low speed as the windings pass extra-strong magnets. Our tests show the R27 maxing out at nearly 4000 RPM, while the R24’s smaller fan astoundingly exceeds 7600 RPM - keep those fingers away!

Noctua NH-U9DX i4

Noctua offers its dual 92mm-fan, single-tower cooler in a variety of model numbers, including the desktop NH-U9B with universal mounting kit, the NH-U9DX i4 with Square and Narrow ILM brackets for LGA 2011 and 1356, and the NH-U9D0 A3 for AMD’s sockets G34, C32 and F. Mounting brackets are the only things that separate these three variations. The company offered us the NH-U9DX i4, but ended up sending the U9B with all the brackets needed to convert it into the U9DX i4 or U9D0 A3.

Knowing that NH-U9DX i4 buyers won’t get all those other brackets, I turned the box around backwards to hide the model number and put only the parts they will receive in the photo. These include:

  • Square ILM mounting bracket set that also fits standard desktop LGA 2011 and 2011-v3 boards
  • longitudinal Narrow ILM bracket set
  • transverse Narrow ILM bracket set
  • fan splitter cable
  • two resistor wires for reducing fan speed
  • tube of Noctua’s NT-H1 thermal compound
  • screwdriver

Photos we’ve seen have shown this version of the cooler delivered with the Square ILM brackets pre-attached, but we took the base photo before adding those, so you can see how well Noctua polishes the mating surface, and how flat it is by the minimal ripples in its reflection.

We selected the longitudinal brackets for our installation, since transverse mounting doesn’t work as well with most cases. Motherboard and case design are both factors in this decision though, and some boards even have the socket turned sideways.

Noctua admits that 32mm of DIMM clearance is the biggest limitation for the NH-U9DX i4, but that’s not much of a limit since most sever and workstation memory is standard profile. We’re likewise using standard profile desktop memory in this motherboard, and a comparison of our own DIMM height to the remaining space shows that users get 35mm of clearance.

How We Tested

Two of the Narrow ILM coolers in today’s test don’t even fit Square ILM sockets, so the only way we could test these is to put them on the board for which this article was conceived, ASRock’s X99E-ITX/ac. The rest of our standard cooling test platform remains relatively intact, minus the closed case and half the RAM.

Test System Configuration

Software And Drivers

GraphicsNvidia GeForce 347.52
ChipsetIntel INF

Benchmark Suite

Prime95v27.9, AVX FFT length 8K, continuous for at least 2 hours
RealTemp 3.70Maximum Temperature, All Cores Averaged
Galaxy CM-140 SPL MeterTested at 1/4 m, corrected to 1 m (-12 db), dB(A) weighting

Comparison Coolers


Conspiracy theories and accusations fly in our response thread whenever we don’t include Noctua’s NH-D15, but it doesn’t fit Narrow ILM boards. Or does it?

While it obviously wouldn’t fit a case in this configuration, we were able to install the NH-D15 by using the bracket set from the NH-U9DX i4. Its heat pipes push against the blank side of our single-sided DIMM, but not hard enough to cause it to lose contact. Better still, if you’re using a tall cube-shaped gaming case with a side intake and lots of space, we found that the slightly-smaller NH-D14 fits in the shown orientation without pushing on the RAM, due to its ¼”-narrower heat pipe spacing. Both the D14 and D15 have adequate clearance between the heat sink and graphics card when installed as shown on the ASRock X99E-ITX/ac. Besides, Noctua loves to respond to bracket requests, or is that only when we ask (let us know)?

Test Results

Dynatron uses thick fans with heavy duty motors to produce high air pressure through narrowly spaced fins, yet even its powerful 80mm cooler can’t stand up to the cooling capacity of Noctua’s 92mm NH-U9DX i4. Dynatron’s fans also override motherboard fan settings, making it impossible to hold a moderate fan speed if the CPU is even a little warm.

Those high RPM numbers referenced earlier in this article are shown here, with the R27 running over twice as fast as the NH-U9DX i4, and the R24 running nearly twice as fast as the R27. Then again, the NH-U9DX i4 has twice as many fans, so it certainly could be half as noisy.

Decibels are a logarithmic scale, so an increase of ten decibels has twice the sound pressure level. That means the R27 is nearly four times as noisy as the NH-U9DX i4, and the R24 is nearly twice as noisy as the R27. And, because the fans of these coolers kick up to full speed on a whim, you’ll rarely find any peace with the R24.

Designed for use in a server room where nobody actually lives, the Dynatron coolers heavily skew the cooling-to-noise scale. The NH-U9DX i4 surprisingly reaches around 77 percent of its big brother’s acoustic efficiency.

Value Analysis

With a similar weight and more tightly spaced fins to provide similar surface area, we really expected the Dynatron R27 to provide similar cooling performance compared to the NH-U9DX i4. The Noctua has two slightly larger fans, but these operate slowly, and Dynatron attempts to make up the difference by using a thicker, higher-pressure fan. Unfortunately, the combination of tight fins and a high-pressure fan didn’t give it the desired level of cooling performance.

The tiny R24 even had lower temperatures than the R27, though not by much. Had the goal of this review been to find something for the server room, I could have called the R24 the best 2U cooler for Narrow ILM, but it’s just too noisy for consumer PCs. Any attempt to balance cooling to noise via fan speed modulation failed, as the cooler ignored the PWM signal and went full force any time the CPU got warm. It could be useful in a home media server in the basement, but that’s usually a place where space is no longer a concern.


Dynatron R24

Priced 40 percent less than the NH-U9DX i4, the R27 still only reaches a value point of one percent below the average of all four coolers. The best 3U cooler in today’s test, noise concerns prevent us from recommending the R27 to PC users. The R27’s fan ignored the PWM signal whenever the CPU got slightly warm, and kicked the motor up to full speed. Most users can tolerate a 49db fan for no more than a few minutes, and persistent rather than peak noise forces us to again call this a server room part.

Dynatron R27

The NH-U9DX i4 is the clear winner in value, noise and cooling power, approaching its non-Narrow ILM sibling in all three areas. Problem spots include a five-inch height that slightly exceeds 3U limits, and 32mm to 35mm of maximum clearance for the nearest DIMM. Because its performance level is so much higher than those of the two preceding parts, we recommend that builders select their DRAM and cases around this cooler rather than get stuck with a hotter, noisier machine.

Noctua NH-U9DX i4

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Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware, covering Cases, Cooling, Memory and Motherboards. Follow him on Twitter.

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