Thermalright SI-128: Evolution of a Past Master

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TESTING


On the test bench...

Testing was done according to our unique heatsink testing methodology, and the reference fan was profiled using our standard fan testing methodology. A quick summary of the components, tools, and procedures follows below.

Key Components in Heatsink Test Platform:

Test Tools

  • Seasonic Power Angel for measuring AC power at the wall to ensure that the heat output remains consistent.
  • Custom-built, four-channel variable-speed fan controller, used to regulate the fan speed during the test.
  • Bruel & Kjaer (B&K) model 2203 Sound Level Meter. Used to accurately measure noise down to 20 dBA and below.
  • Various other tools for testing fans, as documented in our standard fan testing methodology.

Software Tools

  • SpeedFan 4.31, used to monitor the on-chip thermal sensor. This sensor is not calibrated, so results are not universally applicable; however,
  • CPUBurn P6, used to stress the CPU heavily, generating more heat that most realistic loads. Two instances are used to ensure that both cores are stressed.
  • Throttlewatch 2.01, used to monitor the throttling feature of the CPU to determine when overheating occurs.

Noise measurements were made with the fan powered from the lab 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 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. Every fan was tested at four voltages: 5V, 7V, 9V, and 12V, representing a full cross-section of the fan's airflow and noise performance.

The ambient conditions during testing were 19 dBA and 20°C.

TEST RESULTS


Thermalright SI-128 with Reference fan
Fan Voltage
Temp
°C Rise
°C/W
Noise
12V
41°C
21°C
0.27
22 dBA@1m
9V
46°C
26°C
0.33
~19 dBA@1m
7V
49°C
29°C
0.37
<19 dBA@1m
5V
54°C
34°C
0.44
<19 dBA@1m
Load Temp: CPUBurn for ~20 mins.
°C Rise: Temperature rise above ambient (19°C) at load.
°C/W: Temperature rise over ambient per Watt of CPU heat, based on the amount of heat dissipated by the CPU (measured 78W).
Noise: SPL measured in dBA@1m distance with high accuracy B & K SLM

The SI-128 performed acceptably well at every level except 5V, when the temperature began to jump up. A cooler processor (including most Core 2 Duo chips) would probably be fine with good system airflow, but hotter chips will probably require more airflow.

Besides, there is little acoustic difference between 5V and 7V when using our reference fan, so there is very little benefit to running the fan this slowly anyway. At 7V, the cooling performance was good enough for the majority of mainstream processors. Bleeding-edge overclocking chips like the QX6800 or the FX-74 will probably require more airflow — but these are exceptions, not the norm.

Performance at higher airflow levels continued to improve temperatures a bit, but the improvement came at the expense of increased noise from our reference fan. Given the level of performance already achieved at 7V, there's probably not much point in running an increased fan speed.

VS. THE HEAVYWEIGHTS

Heatsink Comparison: Heavyweight heatsinks & SPCR's 120mm Reference Fan
Fan Voltage
Thermalright
SI-128
Thermalright
XP-120
Thermalright
Ultra-120
Scythe
Ninja
°C Rise
°C/W
°C Rise
°C/W
°C Rise
°C/W
°C Rise
°C/W
12V
21
0.27
25
0.32
15
0.19
14
0.18
9V
26
0.33
26
0.33
17
0.22
16
0.21
7V
29
0.37
28
0.36
21
0.27
17
0.22
5V
34
0.44
34
0.44
26
0.33
21
0.27

A comparison against the current high-end heatsinks and Thermalright's old XP-120 confirms the SI-128's position. For most of the lower-airflow points, the SI-128 performed no better than the original XP-120 that is two generations old.

The one point where the SI-128 did perform significantly better was with the fan at 12V, which suggests that the SI-128 was held back by our slow reference fan. The densely spaced fins are not ideal for high performance with low airflow, and it's quite likely that we did not have enough airflow to reach the SI-128's "sweet spot" during our testing.

Some readers might balk at the above comments and ask why a higher airflow fan was not used. The answer is that in our heatsink reviews, we're always interested not in ultimate cooling performance, but performance at low noise levels. With a high speed fan, the SI-128 may provide the best cooling of all the heatsinks mentioned, but this is irrelevant for SPCR, because the cost will be too high a level of noise.

NOISE RECORDINGS IN MP3 FORMAT

Reference 120mm fan: 5V-7V-9V-12V, 5s Ambient between levels: One Meter, One Foot

Comparatives:

Scythe Infinity: 5V-7V-9V-12V, 5s Ambient between levels: One Meter, One Foot

Arctic Cooling Alpine 64: 5V-7V-9V-12V, 5s Ambient between levels: One Meter, One Foot

Scythe Mine w/ stock fan: 5V-7V-9V-12V, 5s Ambient between levels: One Meter, One Foot

Thermaltake Big Typhoon: 5V-7V-9V-12V, 5s Ambient between levels: One Meter, One Foot

HOW TO LISTEN & COMPARE

These recordings were made with a high resolution, studio quality, digital recording system and are intended to represent a quick snapshot of what we heard during the review. Two recordings of each noise level were made, one from a distance of one meter, and another from one foot away.

The one meter recording is intended to give you an idea of how the subject of this review sound 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. For best results, set your volume control so that the ambient noise is just barely audible. 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 one foot recording is designed to bring out the fine details of the noise. Use this recording with caution! Although more detailed, it may not represent how the subject sounds in actual use. It is best to listen to this recording after you have listened to the one meter recording.

More details about how we make these recordings can be found in our short article: Audio Recording Methods Revised.

FINAL CONCLUSIONS

With a properly chosen fan, the SI-128 is capable of cooling most mainstream processors very quietly. The K8 clip is elegant and quite easy to use; the issues with 775 socket mounting have more to do with Intel's choices than Thermalright's.

However, in a market where the top-dog processors consume no more than 65W and most heatsinks are designed to cope with 130W loads, the low noise, low airflow performance is no longer as impressive as it once might have been. The fact is that there's no shortage of stiff competition, especially at US$50. When the cost of the fan is taken into account, the SI-128 doesn't look like a great deal.

The heatsink market as a whole has evolved past the point where performance is the deciding factor. The SI-128 has good build quality and a convenient K8 mounting system, but that may not be quite enough to set it apart in a crowded marketplace. It's quite good — like a dozen other heatsinks we've reviewed.

As noted in the introduction, it will probably find most of its buyer in the home theater market, where price is no object and tall, high-rise heatsinks are counted out by their size. The SI-128 is just short enough to fit in a HTPC case that supports full-size expansion cards. And, given how poor the airflow is in many HTPC cases, the SI-128 may have a real advantage over the more compact heatsinks out there.

Enthusiasts, overclockers and gamers who don't mind noise may also have fun using a high speed fan with the SI-128. There's little doubt it will perform better with a higher speed fan.

Pros

* Performance with slow, quiet fan good enough for most CPUs
* Elegant K8 bracket
* Provides VRM and MOSFET cooling
Cons

* Socket 775 bracket is awkward and too tight
* No fan included
* Poor value-for-money for silencers
* Not compatible with closed-flange fans

Much thanks to Thermalright for the SI-128 sample.

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Articles of Related Interest

Recommended Heatsinks
SPCR's Unique Heatsink Testing Methodology
SPCR's Standard Fan Testing Methodology
Thermaltake Big Typhoon Heatsink / Fan
Scythe SCNJ-1000 Ninja Heatsink
Thermalright XP-120: First 120mm Fan CPU Heatsink
Thermalright Gets Back on Top with the Ultra-120

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