Scythe Samurai Z CPU heatsink / fan

Cooling
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TESTING


On the test bench...

Test Platform

  • Intel P4-2.8A The Thermal Design Power of this P4-2.8 (533 MHz bus) is 68.4 or 69.7W depending on the version. As the CPU is a demo model without normal markings, it's not clear which version it is, so we'll round the number off to ~69W. The Maximum Power, as calculated by CPUHeat & CPUMSR, is 79W.
  • AOpen AX4GE Max motherboard - Intel 845GE Chipset; built-in VGA. The on-die CPU thermal diode monitoring system reads 2°C too high, so all readings are compensated up by this amount.
  • OCZ DDRAM PC-4000, 512 MB
  • Seagate Barracuda IV 40G 1-platter drive (in Smart Drive)
  • Seasonic Super Tornado 300 (Rev. A1)
  • Arctic Silver Ceramique Thermal Compound
  • Nexus Real Silent 92mm fan
  • Two-level plywood platform with foam damping feet. Motherboard on top; most other components below. Eases heatsink changes and setup.

Measurement & Analysis Tools

  • CPUBurn processor stress software
  • SpeedFan version 4.25 software to show CPU temperature
  • A custom-built variable DC power supply that allows us to dial in exactly what voltage is powering the fan
  • B&K model 1613 sound level meter

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. The heatsinks were tested both with the stock fan and our standard reference fan, a Nexus.

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 18 dBA and 21°C.

TEST RESULTS

Scythe Samurai Z
Fan Voltage
Load Temp
°C Rise
°C/W MP
°C/W TDP
Noise
Stock Fan
12V
39°C
18
0.23
0.26
30 dBA@1m
9V
42°C
21
0.27
0.30
24 dBA@1m
7V
46°C
25
0.32
0.36
20 dBA@1m
5V
53°C
32
0.41
0.46
18 dBA@1m
Reference Fan (Nexus 92mm)
12V
46°C
25
0.32
0.36
22 dBA@1m
9V
53°C
32
0.41
0.46
19 dBA@1m
7V
60°C
39
0.49
0.57
<18 dBA@1m
5V
>75°C
>54
>0.68
>0.78
<18 dBA@1m
Airflow: Measured in Cubic Feet per Minute mounted on the HS
Load Temp:
CPUBurn for ~20 mins.
°C Rise: Temperature rise above ambient at load.
°C/W MP / TDP: Temperature rise per Watt, based on CPU's Maximum Power (79W) or Thermal Design Power (69W) rating (lower is better)
Noise: SPL measured in dBA/1m distance with high accuracy B & K SLM

As we were hoping, the stock fan sounded very similar to the fan included with Scythe's Kamaboko and Katana heatsinks. The fan was quite smooth and tolerated undervolting very well. At full speed it was borderline quiet, but when undervolted it could be made almost inaudible. A slight clicking was audible at close range (and in our audio recordings), but it disappeared when listened to from an ordinary listening distance. The noise character was quite consistent: A smooth hum that changed in pitch and volume with the speed of the fan. Turbulence noise was not really a factor until it reached full speed.

Although the fan itself was quite good, the heatsink as a whole had a tendency to resonate as the fan speed increased. The resonance took the form of a high-pitched overtone that was much more irritating than the fan noise alone. Pressing down on the frame of the fan to eliminate vibration eliminated the resonance. However, it is difficult to think of a way that this could be done permanently without harming the airflow.

At full speed, the Samurai Z performed very well. The 18°C rise from ambient is on par with the Zalman 7000 ° a champion of yesteryear and still a very good performance. Even Intel's 800 and 900 series processors probably have some headroom at this level. However, as mentioned, the noise level was borderline (though much better than the Zalman 7000).

9V was probably the sweet spot for a high-end machine. Cooling performance was still quite good, and the noise level dropped from "borderline quiet" to "quiet enough for most people". Further reductions in fan speed would be moving into fanatic territory.

Unfortunately, the news in silence fanatic territory is not so good. The load temperature increased quite rapidly as airflow was reduced. It's not a bad performer by any means, but there are other heatsinks that do better with super low airflow.

For this reason, the Samurai Z didn't look so good when outfitted with our low airflow reference fan. Performance was borderline at 7V. CPU throttling was observed after about 15 minutes when the fan was run at 5V. Given the difficulty of swapping the fan and the generally good sound quality of the stock fan, most users should stick with the stock fan.



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