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be quiet! Dark Rock 2 Tower Heatsink

The be quiet! Dark Rock 2 is a big tower CPU cooler with an odd 135 mm fan. Unfortunately, our sample has trouble living up to its German manufacturer’s name. Note: Addendum on final page (8), 1 Aug 2012.

July 20, 2012 by Lawrence Lee

Product
be quiet! Dark Rock 2
CPU Cooler
Manufacturer
be quiet!
Street Price
£50 inc. VAT

Given our purview, we take a keen interest in PC components that are marketed as “quiet” or “silent.” Sometimes we exercise a little extra scrutiny on products that include the words in the name. When a manufacturer goes one step further and calls themselves something like be quiet! it perks our interest even more as it implies that everything they make has been and will be designed with noise reduction in mind.

be quiet! is a German company that produces power supplies and cooling solutions for desktop PCs. According to their website, “be quiet! sticks to its name: More than ten years experience in the field of noise reduction and silence make be quiet! products probably the most silent one on the market.” It’s an ambitious claim that we’ll gladly put to the test.


The box.

be quiet! makes their CPU cooler debut at SPCR with the Dark Rock 2, yet another tower heatsink. The box claims it has the proficiency to handle an 180W TDP processor and they also made a point to advertise LGA2011 support. It’s a non too subtle implication that it’s suitable for a heavily overclocked Sandy Bridge Extreme. The heatsink is equipped with one of their signature SilentWings fan, which has a fairly unusual design.


Package contents.

The heatsink is packed in foam while a small accessory box holds the manual, thermal compound, and mounting hardware. The kit supports all of Intel and AMD’s modern desktop sockets and includes a backplate, essentially mandatory for a cooler of this size. The mounting procedure requires the bolts to enter through the back, so the motherboard has to be turned upside-down to facilitate installation. The only way you can mount this heatsink with the motherboard already bolted in the case is if there is a large opening on the motherboard tray giving access to the underside of the board.


The Dark Rock 2.

The heatsink itself doesn’t have a remarkable design, a six heatpipe tower resembling various offerings from many other manufacturers. The entire body is nickel-plated, a popular feature that gives heatsinks a menacing luster. The fan is very distinctive with ridged blades and oddly placed mounting holes (they stick out at the center rather being flush either either edge). It’s also a weird size, 135 mm (137 mm by our measurements).

be quiet! Dark Rock 2: Key Features
(from the product
web page
)
Feature & Brief
Our Comment
Very quiet operation
135mm SilentWings® fan with PWM function for optimized fan speed throughout the entire working range provides the perfect balance between superior cooling and quiet. The specially developed wave shaped contour of the heatsink fins optimizes airflow and avoids noise generating turbulence.
Many manufacturers create a non-uniform surface for the fan to press against, but in our experience, it makes no difference, at least not at low fan speed levels.
Highly effective cooling
Six ultra-high performance heatpipes with an oxygen-free copper layer help to transport the heat directly to the optimal place of the heatsinks.
Standard for high performance heatsinks.
First-class materials
Dark nickel-plated metal surfaces and a solid brushed aluminum cover. A stable backplate ensures secure attachment, even when the computer is being transported.
Nickel-plating gives it a nice sheen and prevents oxidation. Backplates are a necessity for heavy coolers.
Product conception, design and quality control in Germany
3 years warranty
Nice, but how often to heatsinks become faulty?

 

be quiet! Dark Rock 2 Rev.A: Specifications
(from the product
web page
)
Overall dimensions without mounting material (L x W x H) (mm) 97 x 138 x 166
Total weight (kg) 0.86
TDP (W) 180
LGA2011 Yes
Socket compatibility Intel: LGA 775 / LGA 1155 / LGA 1156 / LGA 1366 / LGA 2011
AMD: FM1, AM2 (+) / AM3 (+) / 754/ 939 / 940
Backplate Mounting Yes
Anti vibration fan fixing
Overall noise level (dB(A)) @ 900/1250/100% (rpm) 8.7 / 13.9 / 21.2
Heatsink
Number of fins 44
Fin material Aluminum
Base material Copper
CPU contact surface CNC machined
Heatpipe number, Diameter (mm) Heatpipe number, Diameter (mm) 6x 6
Surface treatment Aluminum / Dark nickel-plated
Fan
Fan dimensions (mm) 135 x 135 x 25
SilentWings Yes
Speed @ 100% PWM (rpm) 1300
Air flow @ 12V (cfm, m3/h) 57.9 ; 96.8
Air pressure @ 12V (mm H2O) 1.64
Bearing type Fluid Dynamic Bearing
Rated voltage (V) 12
Input current (A) 0.25
Input power (W) 2.64
Connector 4-pin PWM
Cable length (mm) 200
Lifespan (h / 25°C) 300,000

PHYSICAL DETAILS & INSTALLATION

The be quiet! Dark Rock 2 is composed of a copper base, 6 x 6 mm thick copper heatpipes friction-fit to to 44 aluminum fins, all nickel-plated. The heatsink measures 165 mm tall, but the effective height may be greater depending on how high the fan is mounted. According to our digital scale, It weighs approximately 890 grams or 720 grams without the fan and clips.


The heatsink is quite thick, measuring 71 mm across without the fan; we’re surprised it doesn’t have a dual fan option. The clips used to mount the fan are very tight, so taking it off frequently will scuff up the side.


The fan is unusual in a number of ways but the biggest difference is the location of the mounting holes. The corners stick out at the center of the housing which means it’s not interchangeable with standard 120/140 mm models.


A thick, stylish aluminum plate at the top keeps everything in place.


The fins measure 0.38 mm thick with 2.22 mm gaps separating them, on average, ideal for low airflow/noise cooling. A single, small column of holes has been punched through at the center. The heatpipes are staggered so they each receive more equal airflow around them.


The fins have wavy edges and sinks inward near the center, an attempt to reduce the turbulence produced by the interaction between the fan and the heatsink surface.

BASE & INSTALLATION

The most critical aspect of installation is that the heatsink be securely
mounted. A firm mating results in good contact between the heatsink’s base and
the CPU heatspreader and more efficient heat conduction. Ideally it should
also be a simple procedure with the user having to handle as few pieces of
hardware as possible.


At first glance, the base seems like a typical nickel-plated base with a mirror polish. When we pressed a straight edge against it however, we found that the surface was flat at the center in the direction parallel with the heatpipes but convex in the perpendicular direction.


The Dark Rock 2 uses an unremarkable backplate mounting system that requires bolts to be inserted through the back (the motherboard has to be flipped upside-down). Plastic spacers that grip around the bolts prevent over-tightening and helps ensures equal pressure.


The problem with these types of systems is the mounting clips have to be attached very securely to the base or when the bolts are tightened, they may bend downward. Thankfully this wasn’t an issue in this case.


Fully installed on our LGA1366 test platform.


Like most large tower coolers, the fan hangs over the first memory slot of our test board. There was 51 mm of space underneath the heatsink, but memory clearance depends on how high/low the fan is positioned relative to the heatsink.

TESTING

Before thermal testing, we took some basic physical measurements.

Approximate Physical Measurements
Weight
720 g
890 g with stock fan and clips
Height 165 mm
Fin count 44
Fin thickness
0.38 mm
Fin spacing
2.22 mm
Vertical Clearance*
51 mm
* measured from the motherboard PCB to
the bottom fin of the heatsink

 

Large Heatsink Comparison:
Average Fin Thickness & Spacing
Heatsink
Fin Thickness
Fin Spacing
Thermalright HR-01 Plus
0.45 mm
3.15 mm
Scythe Ninja 3
0.39 mm
2.64 mm
Noctua NH-U12P
0.44 mm
2.63 mm
Noctua NH-C12P
0.47 mm
2.54 mm
Noctua NH-D14
0.43 mm
2.33 mm
Thermalright Archon SB-E
0.49 mm
2.33 mm
be quiet! Dark Rock 2
0.38 mm
2.22 mm
Prolimatech Armageddon
0.51 mm
2.08 mm
Prolimatech Megahalems
0.50 mm
2.00 mm
Zalman CNPS10X Quiet
0.40 mm
2.00 mm
Scythe Kabuto & Zipang 2
0.34 mm
1.94 mm
NZXT Havik 140
0.41 mm
1.91 mm
Scythe Mugen-2
0.31 mm
1.89 mm
Swiftech Polaris 120
0.43 mm
1.85 mm
Thermalright Venomous X
0.53 mm
1.84 mm
Noctua NH-C14
0.38 mm
1.79 mm
Scythe Yasya
0.32 mm
1.78 mm
Cogage TRUE Spirit 1366
0.40 mm
1.70 mm
Arctic Cooling Freezer Xtreme Rev.2
0.30 mm
1.70 mm
Scythe Grand Kama Cross
0.38 mm
1.66 mm
Reeven Kelveros
0.47 mm
1.61 mm
Zalman CNPS9900 MAX
0.16 mm
1.59 mm
Thermalright Silver Arrow
0.32 mm
1.57 mm
Cooler Master Hyper 212 Plus
0.43 mm
1.54 mm
Thermalright Ultra-120 eXtreme Rev.C
0.56 mm
1.52 mm
Zalman CNPS10X Extreme
0.42 mm
1.50 mm

Testing on larger heatsinks are done on our
LGA1366 heatsink testing platform
, while smaller coolers tackle our LGA1155 heatsink testing platform. A summary of the test system
and procedure follows.

Key Components in LGA1366 Heatsink Test Platform:

  • Intel Core i7-965 Extreme
    Nehalem core, LGA1366, 3.2GHz, 45nm, 130W TDP.
  • Asus
    P6X58D Premium
    ATX motherboard. X58 chipset.
  • Asus
    EAH3450 Silent
    graphics card.
  • Intel
    X25-M
    80GB 2.5″ solid-state drive. Chosen for silence.
  • 3GB QiMonda
    DDR3 memory. 3 x 1GB DDR3-1066 in triple channel.
  • Seasonic X-650 SS-650KM
    650W ATX power supply. This PSU is semi-passively cooled. At the power levels
    of our test platform, its fan does not spin.
  • Arctic Silver
    Lumière
    : Special fast-curing thermal interface material, designed
    specifically for test labs.
  • Noctua 140 mm fan (used when possible with heatsinks that fit 140x25mm
    fans)
  • Nexus 120 mm fan (used when possible with heatsinks that fit 120x25mm
    fans)
  • Nexus 92 mm fan (used when possible with heatsinks that fit 92x25mm
    fans)

The systems are silent under the test conditions, except for the CPU cooling
fan(s).

Normally, our reference fans are used whenever possible, the measured details
of which are shown below.

Reference Noctua 140mm fan
Anechoic chamber measurements
Voltage
SPL@1m
Speed
12V
28~29 dBA
1250 RPM
9V
21 dBA
990 RPM
7V
15~16 dBA
770 RPM
6V
13 dBA
660 RPM

 

Reference Nexus 120mm fan
Anechoic chamber measurements
Voltage
SPL@1m
Speed
12V
16 dBA
1100 RPM
9V
13 dBA
890 RPM
7V
12 dBA
720 RPM

 

Reference Nexus 92 mm fan
Anechoic chamber measurements
Voltage
SPL@1m
Speed
12V
16 dBA
1470 RPM
9V
12 dBA
1150 RPM

Measurement and Analysis Tools

  • Extech 380803 AC power analyzer / data logger for measuring AC system
    power.
  • Custom-built, four-channel variable DC power supply, used to regulate
    the fan speed during the test.
  • PC-based spectrum analyzer:
    SpectraPlus with ACO Pacific mic and M-Audio digital
    audio interfaces.
  • Anechoic chamber
    with ambient level of 11 dBA or lower
  • Various other tools for testing fans, as documented in our
    standard fan testing methodology
    .
  • SpeedFan,
    used to monitor the on-chip thermal sensors. The sensors are not calibrated,
    so results are not universally applicable. The hottest core reading is used.
  • Prime95,
    used to stress the LGA1366 CPU heavily, generating more heat than most real applications.
    8 instances are used to ensure that all 4 cores (with Hyper-threading) are
    stressed.
  • CPU-Z,used to monitor the CPU speed to determine when overheating occurs.
  • Thermometers to measure the air temperature around the test platform
    and near the intake of the heatsink fan.

Noise measurements are made with the fans powered from the lab’s variable DC
power supply while the rest of the system was off to ensure that system noise
did not skew the measurements.

Load testing was accomplished using Prime95 or CPUBurn to stress the processor, and the
graph function in SpeedFan was used to ensure that the load temperature is stable
for at least ten minutes. The temperature recorded is the highest single core
reading. The stock fans were tested at various voltages to represent a good
cross-section of airflow and noise performance.

The ambient conditions during testing were 10~11 dBA and 21~23°C.


STOCK FAN MEASUREMENTS

Specifications: be quiet! Dark Rock 2
Manufacturer
Power Rating
3.0 W
Model Number
BQT T13525-MF-PWM
Airflow Rating
57.9CFM
Bearing Type
?
Speed Rating
1,300 RPM
Corners
Open
Noise Rating
21.2 dBA
Frame Size
137 x 137 x 25 mm
Header Type
4-pin
Fan Blade Diameter
128 mm
Starting Voltage
< 5.0 V
Hub Size
47 mm
Weight
170 grams
Data in green cells provided by the manufacturer
or observed; data in the blue cells were measured.

The Dark Rock 2’s stock fan has a very interesting design. It’s slightly smaller than a 140 mm model, its blades have ridges, and the circular frame has a soft, rubberized rim, possibly for dampening. The hub is unusually large, measuring 47 mm across; most 140 mm fans have a hub diameter of ~40 mm. The cable is short, measuring only 20 cm.

Stock Fan Measurements
Voltage
Speed
SPL@1m
12V
1280 RPM
24 dBA
10V
1020 RPM
19 dBA
9V
770 RPM
15 dBA
8.5V
630 RPM
13 dBA
8V
480 RPM
12 dBA
7V
350 RPM
<11 dBA
Measuring mic positioned 1m at diagonal angle from
the center of the heatsink.
Ambient noise level: 10~11 dBA.

The stock fan is more finely controlled when PWM is used; with voltage control, the stock fan is only audible above 7V. Its motor produces a low pitched hum that increases in intensity almost proportionally with the fan speed. It’s not particularly pleasant, but it’s consistent, not developing any odd tones or quirks at different speed levels. At higher fan speeds, it generates more turbulent noise but this is true of all fans.


At 10V, the stock fan can be considered quiet, generating a noise level of 19 dBA@1m.

The fan has some tonal elements, particularly at ~350 Hz.

TEST RESULTS

be quiet! Dark Rock 2
Fan Voltage
SPL@1m
Temp
°C Rise
Stock Fan
12V
24 dBA
66°C
46
10V
19 dBA
68°C
48
9V
15 dBA
72°C
52
8.5V
13 dBA
75°C
55
8V
12 dBA
81°C
61
Reference Noctua 140mm Fan
12V
28 dBA
66°C
46
9V
21 dBA
69°C
49
7V
15 dBA
71°C
51
6V
12~13 dBA
73°C
53
Reference Nexus 120mm Fan
12V
15 dBA
68°C
48
9V
13 dBA
70°C
50
7V
11~12 dBA
72°C
52
°C Rise: Temperature rise above ambient (20°C)
at load.

The Dark Rock 2’s cooling proficiency is not great for a heatsink of its size. The better coolers we’ve tested over the years typically do not exceed a thermal rise above ambient of 50°C on our test platform, even at close to inaudible noise levels. The Dark Rock 2, with its stock fan at 8V measuring just 12 dBA@1m, exceeded 60°C above ambient, and the result at full speed was only 46°C.

Though the Dark Rock 2 doesn’t have a mounting option for a standard 120/140 mm fan, we Jerry-rigged both our reference Noctua 140 mm and Nexus 120 mm fan to it anyway, to see if the stock fan was part of the reason for its poor performance. CPU cooling was fairly similar with the Noctua, except for a significant improvement at the 12~13 dBA@1m level. The smaller Nexus fan performed noticeably better (as it tends to do) but not enough to save the heatsink from being classified as subpar.


Thermal compound footprint.

Disappointed by the results, we checked the thermal compound footprint after testing and discovered the heatsink wasn’t making very good contact with the processor, indicated by the noticeable “branching” pattern that was produced. There was also more excess TIM on the sides due to the base’s uneven surface which we mentioned earlier.

In attempt to create more pressure, we re-tested the heatsink without the plastic spacers that were placed between the mounting clips and the motherboard PCB but the results were the same.

Heatsink Comparison Table

CPU Coolers (ref. 140mm fan): °C Rise Comparison
Heatsink
Fan voltage / SPL @1m*
9V
7V
6V
18~21 dBA
13~16 dBA
11~13 dBA
Thermalright Archon SB-E
37
40
42
Prolimatech Armageddon
39
42
45
Thermalright Venomous X Silent Edition
40
43
44
NZXT Havik 140
40
43
47
Noctua NH-C14
(top mounted)
40
44
48
Noctua NH-C14
40
44
49
Thermalright Silver Arrow
39
45
49
be quiet! Dark Rock 2
49
51
53
*Note: there are minor differences in measured SPL due to the variety of fan orientations and mounting methods offered by the compared coolers.

When using our reference 140 mm fan, the Dark Rock 2 sinks like a rock, ending up at the bottom of our chart, trailing the leading Thermalright Archon SB-E by more than 10°C.

CPU Coolers (ref. 120mm fan): °C Rise Comparison
Heatsink
Fan voltage / SPL @1m*
12V
9V
7V
15~16 dBA
12~13 dBA
11~12 dBA
Thermalright Ultra-120 eXtreme Rev.C
38
40
43
Thermalright Venomous X
38
41
43
Prolimatech Megahalems
38
41
44
Noctua NH-U12P
39
42
44
Scythe Mugen-2
39
42
45
Cogage TRUE Spirit 1366
40
42
45
Prolimatech Armageddon
40
42
46
Zalman CNPS10X Quiet
40
43
46
Noctua NH-C14
39
42
48
Scythe Yasya
41
43
47
Thermalright Ultra-120 eXtreme
40
43
48
Cooler Master Hyper 212 Plus
41
44
48
Thermalright Archon SB-E
42
43
49
Thermalright Ultra-120
42
45
49
Titan Fenrir
43
46
50
Scythe Ninja 3
44
47
49
Noctua NH-C12P
43
47
51
Zalman CNPS10X Extreme
43
47
53
Swiftech Polaris 120
46
49
54
Zalman CNPS10X Flex
45
50
54
be quiet! Dark Rock 2
48
50
52
Cooler Master V8
46
50
54
Reeven Kelveros
47
51
55
Scythe Grand Kama Cross
45
52
57
Antec Kühler H20 620
(pump at 7V, almost inaudible)
52
52
53
Arctic Cooling Freezer Xtreme Rev.2
49
52
58
Scythe Kabuto
51
53
60
*Note: there are minor differences in measured SPL due to the variety of fan orientations and mounting methods offered by the compared coolers.

Unfortunately for be quiet!, our Nexus 120 mm fan results gives us more perspective. We’ve only encountered one traditional tower heatsink with worse performance, the Reeven Kelveros.

MP3 SOUND RECORDINGS

These recordings were made with a high
resolution, lab quality, digital recording system
inside SPCR’s
own 11 dBA ambient anechoic chamber
, then converted to LAME 128kbps
encoded MP3s. We’ve listened long and hard to ensure there is no audible degradation
from the original WAV files to these MP3s. They represent a quick snapshot of
what we heard during the review.

These recordings are intended to give you an idea of how the product sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn’t hear it from
one meter, chances are we couldn’t record it either!

The recording starts with 5~10 second segments of room ambiance, then the fan
at various levels. For the most realistic results, set the volume so that
the starting ambient level is just barely audible, then don’t change the volume
setting again.

TESTING REDUX – by Mike Chin

be quiet! was shown a preview of this review a week ago, and their reaction was that we should have notified them immediately about such sub-par results. They’d received positive reviews from several other hardware sites, and were certain that our results were due to a substandard sample that managed to slip by their QA. So, we decided to give them a second chance, and they express-shipped over two more samples of the same HSF.

Both of the new samples were tested… with virtually identical results as the first one.

With sample #2, at full fan speed, cooling improved by maybe 1°C, but at lower fan speeds, it was worse by 1-2C. It’s safe to say there was no appreciable difference in performance. Sample #3 was worse, up to 5°C worse at full 12V fan speed. No further testing was done on that sample.

Both of the new sample bases were checked for flatness using a metal straight edge ruler. Like the first sample, neither of the new samples had flat bases. The base of sample #2 was not flat, but it was not consistently convex, much like sample #1. With sample #3, the straight edge made contact with only the rim of the base, leaving a tiny but constant gap through the middle.

There was no sign of damage in any of the heatpipes in any of the 3 samples.

If pressed to find a reason why these products don’t perform as well as they look like they should, I’d examine….

1. the flatness of the base. I think this is probably the #1 problem.
2. the strength of the brackets that screw into the base of the heatsink — they may bend too easily under stress, which means the tension between the HS base and the CPU is not high enough
3. the quality of the heatpipes. I know from experience that all heatpipes are NOT equal.
4. the integrity of the joints between heatpipes and fins, and between heatpipes and the base

 

FINAL THOUGHTS

The be quiet! Dark Rock 2 has the look of a heavy duty heatsink from Thermalright, Prolimatech, or Noctua, but unfortunately that’s as far as the resemblance goes. Its performance is decidedly poor compared to today’s various high-end 140 mm fan CPU coolers. be quiet!’s ambitions were sunk by mounting system that doesn’t generate enough pressure and a terribly uneven base. The latter may well be a manufacturing defect, but it doesn’t bode well for retail samples if they can’t get a review unit right.

Even if performance wasn’t an issue, there are other flaws we can’t ignore. Despite the manufacturer’s name, the stock SilentWings fan suffers from an undesirable low-pitched hum throughout its range. The fan clips are designed to accommodate the stock fan’s oddly placed mounting holes, so you can’t swap in a standard 120/140 mm model without modification. Furthermore, for such a thick cooler, we were surprised to find a second fan is not included, or at least the option for one. We’re also not fond of the installation scheme which requires flipping the motherboard upside-down.

Most of be quiet!’s sales occur in Europe; in the UK, the Dark Rock 2 sells for approximately £50 inc. VAT which is quite steep given its capabilities. We can’t recommend it as there are numerous competing coolers on the market that offer far greater value with fewer issues than the Dark Rock 2. It does have one advantage as many of its competitors haven’t yet been updated to support LGA2011. However, if you have the financial latitude to purchase a Sandy Bridge Extreme platform, you’d likely have no trouble shelling out a little extra for a truly excellent heatsink like the Thermalright Archon SB-E.

Our thanks to be quiet! for the Dark Rock 2 CPU cooler sample.

* * *

ADDENDUM #2: The real Final Word

* * *

SPCR Articles of Related Interest:

SpeedFan: A Guide to Universal Motherboard Fan Control
Reeven Kelveros & Arcziel CPU Coolers
Thermalright Archon SB-E 15cm Fan CPU Cooler
Scythe Big Shuriken 2 & Reeven Vanxie CPU Coolers
Fans from Noctua & Corsair at Computex 2012
SPCR’s Updated 2012 Small CPU Heatsink Test Platform

* * *

Discuss
this article in the SPCR forums.

ADDENDUM — 1 Aug 2012: The Real Final Word by Mike Chin

The comments in the forum discussion of this review provoked further communication between bequiet! reps and myself. The last email query was whether our voltage control of the bequiet! PWM fans might have affected the results. I pointed again to our carefully controlled and identical setups for testing and comparison, using either RPM or SPL as reference points. The comparison table in the review makes it very clear. I also reiterated my position that the non-flat, somewhat concave profile of the base was, in my opinion, the #1 weakness, which might be exacerbated by less than ideal pressure between the base and the CPU.


Here is the imprint of the TIM on the CPU and the base of the Dark Rock 2 from the last sample tried and tested. The striations of the TIM mean that the TIM was not sandwiched tightly between the two surfaces, and thus floated a bit to make this pattern. But because the TIM does not cover the entire surfaces of the base and the CPU, it’s hard to see that along the top and bottom edges, the TIM has actually been pressed out, and there’s much less of it remaining — this is as it should be in the center.

I decided to test my hypothesis one last time. This time, rather than use the stock bequiet! mounting hardware, I borrowed the rigid, heavy-duty, machined brackets and bolts from a Prolimatech Megahalems cooler. This is probably the best mounting hardware I’ve come across during my >15 years of playing around with CPU heatsinks. Most of the Thermairight and Noctua CPU cooler mounting hardware is just about as good, but what’s particularly useful about the Megahalems hardware is that it is easy to use with many other tower heatsinks.


Here is a photo of the complete Megahalems mounting hardware. The bottom left bar clamps over the base of the heatsink with the next two bars bolted firmly to the motherboard on either side of the heatsink base. An enormous amount of pressure can be brought to bear on the CPU/base contact area.


The bequiet! cooler mounted with the Megahalems hardware.


The bar goes over the base of the tower heatsink, and the spring-loaded bolts on either end are tightened to firmly press the heatsink down onto the CPU. The spring-loaded bolts were not completely tightened yet in this photo. Because the base of the Dark Pro 2 is a little thicker and wider than the Megahalems for which the mounting hardware was designed, the fit was extremely tight, and the pressure on the base/CPU interface was super high once the spring-loaded screws were tightened all the way. I kept my finger crossed that the motherboard would not sustain microscopic damage in its multi-layer signal traces — this has happened before, killing the motherboard. Luckily, no such damage seems to have been sustained.

The end result was virtually identical to previous results, with an improvement of perhaps 1°C over the best result we recorded for the three samples in previous tests. Time to examine the TIM imprint.


This time, you can clearly see that there is a line on the top and bottom edges of the heatsink, matched on the CPU, where the TIM has been pressed away, due to the high pressure of the Megahalems mounting hardware. Yet, with all that pressure, the TIM in the center still has those fractal-like striations. This is conclusive evidence that the base of the bequiet! Dark Pro 2 sample here is concave.

There’s no question why all the added pressure of the Megahalems mounting did not make any improvement in cooling performance; the center of the base was still not tightly pressed against the CPU because the base of the cooler is concave. Only the edges made tight contact, but that’s not where the heat of the CPU is concentrated, it is in the center. This is the primary reason that the three Dark Pro 2 samples all have such mediocre cooling performance.

One last point: An electronic, infrared, non-contact thermometer was used to check the temperature of various points on the heatsink during the above thermal test. With room ambient at 24°C, and the CPU core reporting 70°C, none of the fins read any higher than ~30°C, and the hottest portion of the heatpipes right at the base of the heatsink read just 37°C, My conclusion: Much of the heat from the CPU was simply not getting into the heatsink.

A photo of a TIM imprint on the base/CPU of a high performance cooler would really put the matter to rest, so here it is.


Desired TIM imprint.

The heatsink was turned 90 degrees for the above photo, and the TIM was smuged a bit during uninstallation, but you can clearly see the matching imprints of the TIM on the base and on the CPU. Both have a central area where there is very little TIM; it’s been pushed from the center due to very tight contact. Only around the periphery are there any striations of the TIM. Incidentally, this is a new photo taken just for this addendum, and the heatsink is the original Megahalems sample we tested a couple years ago. Its performance here was 12°C better than the bequiet! Dark Pro 2, with the latter’s stock fan at full speed.

Case closed.

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