Heatsink Test – Joe
SUMMARY: A top choice for P4/K8 CPU cooling – with the right setup, can be both quiet and aggressive when needed.
The SI-120 is designed to fit all known Intel P4 motherboards using the stock P4 heatsink retention bracket and AMD K8 motherboards with a supplied adapter. It’s compatible with AMD Athlon64 FX 3200+ (socket 939/940), Athlon64 3200+ (socket 754) and Intel Pentium 4 socket 478, 2.5 GHz and above.
Looking at this from the front
shows five heatpipes coming out of the base. A view from the top
shows why this large heatsink is also quite light – good fin spacing and elegant design to hold everything together – good job Scott! In use, the fan overhangs the fins by about ½” – airflow from the fan will also cool components around the socket, including RAM – a real plus with this design.
The SI-120 ships with parts for P4 and K8 mounting:
The mounting clips securely engage the P4 retention bracket – a very secure system. For K8, the supplied mounting bracket is a P4 mount for K8 motherboards.
The base is well finished:
When I ran my nail over it, I could not feel or hear any ridges (strobe lighting accectuates polishing marks).
The Thermalright SI-120 was tested on an Acorp 4S845A motherboard with a modified P4 1500 to read CPU case temps. I tested the SI-120 with a Delta’s 120 x 25 mm fan (WFB1212HH).
I varied voltages to get a performance range for various fan speeds, measuring rpms using an Omega digital tachometer. I measured fan noise with a Radio Shack sound meter 8″ from the fan’s intake. These are not comparable to noise levels reported by fan manufacturers; noise is usually measured at three feet from the fan.
|SI-120, 2994 rpm, 63 dBA|
|SI-120, 2583 rpm, 59 dBA|
|SI-120, 2006 rpm, 51 dBA|
|SI-120, 1511 rpm, <50 dBA|
|SI-120, 984 rpm, <50 dBA|
¹Die Temp as measured by the P4 on-die diode, per MBM.
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.
Results place the SI-120 in the topmost rank of P4 heatsinks tested to date (Heatsink Ranking). Of particular note is performance at severely reduced fan rpms – the difference under CPU stress is a minimal 4ºC at 100 watts – truly outstanding. Fan noise at 984 rpm is virtually soundless inside a case three feet away.
Thermalright’s SI-120 is an excellent choice for aggressive or low noise P4/K8 CPU cooling. However, the more aggressive the fan used, the higher the noise level – no surprise.
If you want top performance while gaming but almost soundless at other times, I would recommend using an aggressive 120 mm fan with a rheostat – this gives you the best all-around performance capability. For “normal” use, a fan spinning at about 1500 – 2000 rpm will give very good performance at low noise levels.
Disclosure: Joe Citarella has a financial interest in a company developing thermosyphon products for electronic chip cooling.