Thermalright SLK800

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Top rank Socket A heatsink — Joe

SUMMARY: Top Rank socket A cooling, depending on noise preference.

SLK800

A while ago we took a look at the Thermalright SLK600. It’s not a stretch (actually, it was) for Thermalright to come up with an 80mm version, the SLK800.

SLK800

You’ll get some idea of its size with Vantec’s 80mm Tornado fan in the background. The base

Base

is about the same as the SLK600. The base finish is very good – there are no polishing marks on it, although not a polished finish; lapping might improve performance a tad but I think not worth the effort.

One notable factor in the SLK800’s favor is the amount of air flowing down through the fins from the 80mm fan overhanging the heatsink’s sides – the top measures 53 x 82mm. There is a significant secondary cooling benefit as a result, and components around the heatsink should run cooler. In addition, since the motherboard acts as a secondary CPU heatsink, there will be a positive impact on CPU cooling.

The clip mounts on all three of the socket’s lugs – a plus. However, you must use a screwdriver to engage the lugs. I found the clip very stiff and had to push down with my thumb along with the screwdriver to mount it on the socket. As with all screwdriver-assisted mountings, make doubly sure the screwdriver tip is securely in the clip’s slot – a slip under pressure could trash a motherboard.

THE TEST

Readers have been asking for a range of fan speeds when I test heatsinks, so I tested the SLK800 with Vantec’s Tornado, a Sunon 80 x 38mm fan, model #PMD1208PMB1-A rated at 84.1 cfm @ 5700 RPM, 55.2 dBA, 9.1w; this fan features vanes in the base to straighten airflow off the blades. I varied voltage to get a range of fan speeds and measured rpms using an Omega digital techometer.

I measured noise using a Radio Shack sound meter placed 8″ from the fan’s intake and recorded noise at a number of rpms – these should not be far off the mark far other 80mm fans at similar rpms.

Manufacturers meter sound at 3 feet from the fan, so the dBAs I measured do not correspond to the manufacturers ratings. I normalized the readings I found to the manufacturer’s spec for the fan, as shown in the table below.

The SLK800 was first tested on the CPU Die Simulator which gives results that are unaffected by motherboard influences. I then tested it on an Iwill KK266+ and Shuttle AK31, which are modified to read AMD CPU die temps directly, as an example of what users might see on their systems.

TEST RESULTS – CPU Simulator

Heatsink
Die Temp
Ambient Temp
Delta
C/W
SLK800, 5520 rpm, 55 dBA
43.5 C
26.2 C
17.3 C
0.23
SLK800, 5146 rpm, 53 dBA
43.4 C
25.4 C
18.0 C
0.24
SLK800, 4750 rpm, 51 dBA
44.3 C
26.1 C
18.2 C
0.24
SLK800, 4316 rpm, 49 dBA
44.7 C
25.7 C
19.0 C
0.26
SLK800, 3898 rpm, 47 dBA
45.5 C
25.9 C
19.6 C
0.26
SLK800, 3438 rpm, 44 dBA
46.4 C
25.8 C
20.6 C
0.28
SLK800, 2967 rpm, 43 dBA
47.6 C
25.8 C
21.8 C
0.29

TEST RESULTS – Motherboard
CPU/Motherboard

CPU Die

Ambient Temp

Delta

C/W

CPU Back Temp

Iwill KK266+, Palomino 1200, 5780 rpm

36.2 C

26.1 C

10.1

0.19

37.7 C

Iwill KK266+, Palomino 1200, 4472 rpm

36.4 C

26.0 C

10.4

0.19

38.2 C

Iwill KK266+, Palomino 1200, 3015 rpm

38.2 C

26.3 C

11.9

0.22

39.7 C

Shuttle AK31, XP @ 1467, 5700 rpm

38.0 C

21.8 C

16.2

0.25

NA

Delta = CPU temp – Ambient Temp
C/W = Delta / CPU Watts

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 SLK800, running at 5520 rpm, in the top rank of heatsinks (Heatsink Ranking). Note diminishing returns; also note that the performance gap between air and water has disappeared, although the noise gap has widened.

The difference between aggressive cooling/high noise and “reasonable” cooling and noise is about 6 C over 100 watts. For a CPU radiating half that, the difference starts to fade very quickly (note: 38 dBA is the generally accepted noise standard for PCs).

The C/Ws shown here are at high load for at least 30 minutes – the number of times most users even come close to this loading is minimal.

The upshot is that for the AVERAGE user who is not pushing the CPU and spends most of the time for surfing and email, a quiet fan, such as the Vantec Stealth, might do the job OK. Each user must make a choice, balancing cooling needs vs noise tolerance.

CONCLUSIONS

Thermalright’s SLK800 is a fine choice for Socket A cooling. Depending on how aggressive your cooling requirements are, noise can range from the sublime to the ridiculous.

The SLK800 is available from The Heatsink Factory.


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