Microcool NorthPole XE Whisper heatsink/fan

Cooling
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TESTING

Test Platform

  • Intel Pentium M 770 with a measured power draw of 23.3W under CPUBurn. This number includes power efficiency losses in the VRMs on the motherboard.
  • AOpen i915GA-HFS motherboard
  • 2 x 1024 MB Corsair DDR2 RAM
  • Hitachi E7K100 100 GB notebook drive
  • FSP Green PS 400W power supply
  • Arctic Silver Ceramique Thermal Compound
  • Two-level plywood platform with foam damping feet. Motherboard on top; most other components below. Eases heatsink changes and setup.


On the test bench...

Measurement & Analysis Tools

  • CPUBurn processor stress software
  • AOpen PowerMaster software to show CPU temperature, clock speed, and core voltage, as well as fan speed.
  • B&K model 1613 sound level meter


Official SPCR mascot, hard at work.

The two samples of NorthPole XE were tested in a direct comparison with the stock AOpen heatsinks. The tests measure the combined noise of CPU and northbridge fans.

Noise measurements were made with the fan in the power supply temporarily stopped to ensure that it did not affect the results. A notebook drive was used to minimize the effect of extraneous system noise; the ambient noise level was measured while the drive was running.

Load testing was accomplished using CPUBurn to stress the processor. Our usual temperature measurement software, SpeedFan, did not work on the AOpen board, so AOpen's PowerMaster utility was used to read the thermal conditions of the CPU. Unfortunately, no equivalent software could be found to reliably measure the temperature of the northbridge.

The ambient conditions during testing were 20 dBA and 21°C.

TEST RESULTS

Our original intent was to use the Smart Fan settings in the BIOS to adjust fan speed as needed to maintain adequate cooling. Unfortunately, these settings did not seem to have any effect while Windows was running; All fan headers supplied a full 12V in Windows, no matter what settings were used. A software version of the fan controller, called SilenTek, was also downloaded and installed, but it proved to be little better, either running the fan at full speed or not at all, with almost no adjustable range in between. Even SpeedFan let us down ? it would crash the whole system if we tried to force it to run.

Eventually, we decided to run the board in its stock form, with all headers supplying a full 12V. This gives the NorthPole XE a bit of an advantage, since it is thermally controlled internally, independent of its input voltage. Realistically speaking, both heatsinks could be used with SilenTek to cool the processor fanlessly in idle, but the repeated starting and stopping of the fan would be more irritating than constant fan noise.

Microcool NorthPole XE Whisper vs. AOpen stock heatsinks
CPU State
Temperature
Fan RPM
°C Rise
°C/W
Noise
Microcool NorthPole XE Whisper (w/o pads)
Idle (SpeedStep enabled)
28°C
1,400
7
0.30
24 dBA@1m
CPUBurn
61°C
2,700
40
1.72
27 dBA@1m
AOpen stock heatsinks
Idle (SpeedStep enabled)
26°C
3,500
5
0.21
32 dBA@1m
CPUBurn
61°C
3,500
40
1.72
32 dBA@1m
Temperature: In degrees Celsius.
Fan RPM: Fan rotation speed, in rotations per minute
°C Rise: Temperature rise above ambient at load.
°C/W: Temperature rise per Watt, based on CPU's known power dissipation
Noise: SPL measured in dBA@1m distance with high accuracy B & K SLM

*Test stopped for fear of damaging the CPU

Initial testing showed the NorthPole to be a very poor performer. CPU temperature reached 80°C on CPUBurn. Then we started tinkering and noticed that pressing down on the heatsink instantly dropped by >10°C. This suggested that there wasn't enough pressure on the CPU die. The cause was fairly obvious: The pads designed to take protect the edges of the CPU die from pressure during installation were too thick. As a result, the pressure between HS base and die was too low.

The pads were removed, and a second set of tests run. This time, the NorthPole XE turned in acceptable results, almost identical to the stock heatsink. However, the twin NorthPoles were quieter than AOpen's fans, especially in idle. Even with the CPU heavily loaded, however, they remained substantially quieter than AOpen's stock heatsinks.

The fan on AOpen's tiny northbridge heatsink is the worse of the two stock HSF. It generates a shrill whine. If the fan controller on the motherboard worked properly, the northbridge fan would not run at full speed, which would make the noise of the stock cooling system much more palatable. With the northbridge fan temporarily stopped and only the CPU fan running, the noise was roughly the same volume as the NorthPole HSFs at full load. However, it is possible that running the NB fan at a lower speed is not an option because the stock HSF does not provide enough cooling otherwise.

Changes in NorthPole's fan speed were gradual, and only occurred after the processor had been under heavy load for some time. For most usage patterns, the fan should rarely ramp up. Rapid changes in fan speed could be produced by increasing heat transfer by pressing down on the heatsink, but this is hardly typical behavior. However, it does suggest that contact pressure was still not as high as it could have been. We could not monitor the fan speed of the northbridge fan, but we never heard it increase substantially in speed.

There was some intermodulation noise between the fans as they increased and decreased in speed ever so slightly. Another issue was a ringing tone somewhere in the midband; this problem was especially noticeable when the fan sped up under load. Further investigation revealed that the aluminum fan shroud was the culprit. The noise could be eliminated by putting pressure on the shroud to prevent it from resonating. The impact of damping the shroud was significant ? as much as 2~3 dBA@1m under load.

In terms of noise character, the NorthPoles had surprisingly deep voices for such small fans, although the dominant pitch tended to change with distance. From one meter away the primary noise was the resonance mentioned above, but the noise turned into a lower-pitched growl closer in. With the exception of the resonant tone, the noise character did not change a lot under load.

Because the northbridge fan was by far the noisier of the two AOpen coolers, one final test was run using a NorthPole XE on the northbridge and the stock cooler on the CPU. This proved to be the most successful combination. The noise level dropped to 27 dBA@1m in both idle and under load. This is the same noise level as the twin NorthPoles achieved under load ? but the character of the noise was nicer, since the interaction between the two NorthPole fans was absent, as was the resonating shroud. The noise was more broadband and easier to ignore than the two NorthPole fans together. As an added bonus, this solution only costs half as much, since only one NorthPole cooler is needed.



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