Cooling Efficiency Dependence on the Fan Type and Rotation Speed
Here we are going to check how the cooling efficiency of the new Scythe Kabuto cooler depends on the type and rotation speed of the cooling fan. To accomplish this, we tested the cooler in passive mode (no fan), with two 120 x 120 x 25mm Scythe Slip Stream 120 fans and with one 120 x 120 x 38mm SiloenX iXtrema Pro IXP-76-16 fan:
We ran the tests inside the system case with the side panel removed in order not to affect the fans efficiency in any way. Here is the results chart:
As you see, Scythe Kabuto can cope quite well with a Core i7-920 processor in its nominal mode even without a fan, while adding a 120-mm fan at practically noiseless 540RPM lowers the peak CPU temperature by more than 24°C! Moreover, we could overclock our CPU by 42.4% to 3800MHz in the same fan mode. Speeding the fan up to 860RPM and then to 1320RPM lowered the CPU temperature to 81°C and 75°C respectively, and allowed even greater overclocking. The maximum CPU frequency we could hit was 3970MHz at 1.35V Vcore, which I personally consider a very good result. I would also like to say that by replacing the standard 120 x 120 x 25mm fan with a bigger 38mm fan doesn’t have the desired effect even despite the higher rotation speed of the latter (1760RPM vs. 1320RPM). The latter indicates that the cooler heatsink is perfectly optimized for the Slip Stream fans.
Here I would also like to comment on the way the efficiency of a top-cooler depends on the presence or absence of the system case side panel. Tower-coolers which airflow is directed along the mainboard PCB are not as sensitive to this factor (we are talking about system cases with good airflow organization). The top-coolers are way more sensitive to that. Look for yourselves:
It turned out that Scythe Kabuto cools the CPU 4°C better under maximum load when the side panel is removed. Tower-coolers demonstrate half the difference of only 2°C. However, everything we have just said is true for our test system case – Antec Twelve Hundred. The results may vary by system case.