Thermalright SLK600

SUMMARY: Outstanding performance; depending on your noise tolerance, the SLK600 scales very nicely.

The good guys at Thermalright were nice enough to send the production version of their SLK600 (prototype review HERE). I found performance levels similar to those of the prototype, so the translation to production went very well.

I acquired additional test gear that enables me to vary fan voltages - hence rpms. I bought a second lab power supply to vary fan voltage and an Omega tachometer to precisely measure rpms (accurate to +/- 2 rpm).

First, the SLK600 was tested on the CPU Die Simulator which gives results that are unaffected by motherboard influences. Since results are the same as the prototype, you can refer to these tests for motherboard results.

SLK600
Die Temp

Ambient Temp

Delta

C/W

dBA

RPM

Delta 38mm
37.8 C

20.5 C

17.3 C

0.23

52

7500

Delta 38mm
38.1 C

20.4 C

17.7 C

0.24

51

7050

Delta 38mm
38.4 C

20.4 C

18.0 C

0.24

49

6600

Delta 38mm
38.8 C

20.3 C

18.5 C

0.25

48

6100

Delta 38mm
39.4 C

20.3 C

19.1 C

0.26

46

5550

Delta 38mm
40.1 C

20.4 C

19.7 C

0.26

44

5000

Delta 38mm
42.0 C

20.8 C

21.2 C

0.28

40

4400

Delta 38mm
43.4 C

20.8 C

22.6 C

0.30

37

3800

Delta 38mm
45.1 C

20.6 C

24.5 C

0.33

<36

3080

Delta 25mm
42.2 C

20.7 C

21.5 C

0.29

47

6700

Delta 25mm
47.1 C

20.7 C

26.4 C

0.35

36

4250

YS Tech 25mm
45.5 C

20.6 C

24.9 C

0.33

35

4230

Vantec 25mm
54.1 C

20.3 C

33.8 C

0.45

20

2450

Interpreting C/W: For every watt (CPUw) that the CPU consumes, the HSF will limit the CPU's temperature rise to (C/W x CPUw) plus the temperature at the HSF's fan inlet. For example, at an ambient temp of 25 C, a C/W of 0.25 with a CPU radiating 50 watts means that CPU temp will increase 50 x 0.25 = 12.5 C over ambient temp, or 37.5 C. The lower the C/W, the better.

Die Simulator results place the SLK600 at the topmost rank of heatsinks (Heatsink Ranking) using the Delta 43cfm fan at spec. Graphing test results shows the tradeoff between performance and noise:

Note that the Delta 44cfm unit turns in better performance at comparable cfms - the flow straighteners are a plus. The difference between the YS Tech and Delta 38 at 4200 rpm is minimal - an indication that similar fan designs will turn in about the same performance at equal rpms.

Note also that performance is at the expense of noise - the "tolerable" dBA level is 38 dBA, and almost all the points lie above this level. The Vantec Stealth is indeed very low noise, but in the finest traditions of "no such thing as a free lunch", the price is about 20C less cooling compared to the Delta 43cfm unit at spec.

The SLK600 is a top choice for CPU cooling; however, factoring noise considerations and fan selection into the equation may mitigate realized performance.