Arctic Cooling Freezer 7 Pro HSF

Cooling
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TESTING

The Freezer Pro series is not available for socket 478, which means that the test bench that we have used for the past year could not be used. A socket 775 test platform was put together using the parts outlined below. The data from this review cannot be directly compared to the data from past reviews. It also means the test has become a bit tougher because a hotter processor is used. The Pentium 520 used in this test is about the coolest Intel P4 on the market today, but it is still 15-20W hotter than our previous P4-2.8 Northwood.

To establish some references on this test platform with heatsinks that we have already tested and reviewed, we took time to install and run stress tests on the Thermalright XP-120 and the Scythe Ninja, both top performers, as well as a standard Intel socket 775 HSF. This is the cooler that's packaged with Intel's retail processors.

Measurements of the total AC power consumed by the system during the load tests were also recorded, as a check on Arctic Cooling's claim about improved cooling for the VRM. We know that improved cooling for the VRM results in slightly higher efficiency and lower power draw.


On the test bench...

Test Platform

Measurement & Analysis Tools

Noise measurements were made with the fan powered from the lab DC power supply with everything else turned off to ensure minimal ambient noise.

Airflow measurements for this heatsink were not made due to the difficulty of measuring the stock fan accurately. Instead, RPM measurements were made using the onboard monitoring chip and a Zalman Fanmate to vary the input voltage.

Load testing was accomplished using CPUBurn to stress the processor, and the graph function in SpeedFan was used to make sure that the load temperature was stable for at least ten minutes.

The ambient conditions during testing were 17 dBA and 21°C.

TEST RESULTS

Arctic Cooling Freezer 7 Pro with Stock fan
Fan Voltage
RPM
Temp
°C Rise
°C/W MP
°C/W TDP
Noise
(dBA@1m)
AC Power
12V
2400
39°C
18
0.18
0.21
33~37
132W
10V
1800
47°C
26
0.26
0.31
28
132W
9V
1350
53°C
32
0.32
0.38
20
134W
8V
900
67°C
N/A
N/A
N/A
18
138W
7V
<700
throttle
N/A
N/A
N/A
<17
141W
Airflow: Measured in Cubic Feet per Minute mounted on the HS
Load Temp:
CPUBurn for ~20 mins.
°C Rise: Temperature rise above ambient at load.
°C/W MP / TDP: Temperature rise over ambient per Watt of CPU heat, based on CPU's Maximum Power (100W) or Thermal Design Power (84W) rating (lower is better)
Noise: SPL measured in dBA/1m distance with high accuracy B & K SLM
AC Power: Total AC power to system measured with Seasonic Power Angel
Throttle: CPU drops its internal voltage and clock speed to avoid thermal damage. Usually occurs at 75~76°C with this particular processor.

Fan @ 12V: Cooling performance was excellent. A rise over ambient of just 18°C on a CPU that's putting out as much as 100W is pretty good. Whether you use the 100W or 84W rating, the °C/W numbers are very good.

The noise level was oddly variable. The variability came from air turbulence, but it didn't have the more-or-less constant whoosh that most fans exhibit. Instead, it seemed to go up and down in surges, sounding smoother one moment and "stormier" the next, sometimes a bit randomly, and other times in a more regular, cyclical rhythm. Depending on who is listening, this variable effect can be described as either obvious or subtle. (The effect can be heard somewhat in the audio recording at 12V on the next page.) From a meter distance in open air, it could be heard easily in a quiet room, although the overall volume may be more annoying than its variability. The base SPL of 33 dBA@1m is already well above our 30 dBA maximum SPL for a quiet product.

The hum of the motor sounded lower in pitch when there was less turbulence noise. The volume of the noise was reasonable for a fan at full speed, but the variability of the noise emphasized its presence and made it harder to tune out.

We don't know why this fan sounded the way it did. The absence of a frame should have reduced the turbulence, if anything. There were no odd fluctuations of voltage seen in the variable power supply driving the fan, either. Call it a mystery for now. Perhaps AC will send us another sample or two for us to see if this effect is common to other samples.

Fan @ 10V: This is not one of our usual measurement points, but it marked something of a halfway point between the variable noise at 12V, and the barely audible noise level at 9V. The cooling performance of 26°C rise from ambient was still very good. The noise was constant, much smoother than at 12V. Turbulence was less of an issue, and there was a touch of low-frequency growl. The measured noise level of 28 dBA@1m would be considered perfectly acceptable in many environments but unlikely to be below ambient noise in a quiet room.

Fan @ 9V: It was impressively quiet at this level. The noise was broadband, slightly biased towards the lower frequencies. Only a trace of the growl at 10V remained. The 32°C rise from ambient was still acceptable; in <25°C room temperature and a well-built PC system the maximum CPU temp would probably not exceed the low 60s, Celsius. Intel processor typically don't start throttling till ~70°C or higher.

Fan @ 8V: It was difficult to hear the fan even from as close as a couple feet. However, the CPU temperature of 67°C is not acceptable. It would be >70°C if the system was in a PC case.

Fan @ 7V: Virtual silence was achieved. Using a pair of high fidelity headphones at fairly high gain, we were unable to tell the difference between a recording of the Freezer Pro at 7V with our sensitive Taylor Hohendahl Engineering (THE) KP- 6M Reference Microphone just 3" away, and a recording of the ambient room noise ? with no noise sources in the room. However, the CPU temperature soared quickly to 76°C and the CPU throttled.

Given that our Intel 520 is about the coolest of the 775 processors, it's not safe to run the Freezer 7 Pro at less than ~9V in any system. Between 9V and 12V, there is a fairly wide range of cooling and noise options, however.



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