Thermalright SLK 900A

Very good Socket A cooling, depending on noise preference – Joe

SUMMARY: A fine choice for Socket A cooling, although performance will depend on each user’s noise tolerance.

Thermalright 900A

The good guys at Thermalright were nice enough to send Thermalright’s 900A one for a test spin. This version features a return to the “basic” mounting clip, one which engages all three socket lugs; it also requires a screwdriver to mount. The clip is very stiff, so use care when mounting on a motherboard – one slip can trash the mobo.

The base is well finished:


When I ran my nail over it, I could not feel or hear any ridges.


The Thermalright 900A was first tested on the CPU Die Simulator which gives results that are unaffected by motherboard influences. For testing, I used a Delta FFB0812SHE, 68 cfm @ 4800rpm, 48.5 dBA; this features vanes in the base which straighten airflow into the heatsink. I varied rpms to give a range so users can match performance to noise tolerance.



Die Temp
Ambient Temp
Thermalright 900A, 4819 rpm
43.9 C
27.4 C
16.5 C
Thermalright 900A, 3504 rpm
45.9 C
27.4 C
18.5 C
Thermalright 900A, 2009 rpm
51.6 C
28.7 C
23.4 C

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 Thermalright 900A in the topmost rank of heatsinks tested to date (Heatsink Ranking).


Thermalright’s Thermalright 900A is a fine choice for Socket A cooling, although performance will depend on each user’s noise tolerance.

Thanks again to Thermalright for sending this our way. The Thermalright 900A is available from Crazy PC and Heatsink

¹Note that manufacturers measure fan noise usually 3 feet from the fan.

Email Joe