You can see the results of our tests in this table as well as in the following diagram. As opposed to our previous reviews, they are grouped in three temperature ranges for better viewing: below 80°C, 81°C to 90°C, and above 90°C.
It must be noted that the affordable and rather compact coolers from Scythe and Thermalright cope with an overclocked six-core CPU, which is quite an achievement in itself. Of course, $25-30 coolers like the Katana 4 and TRUE Spirit 90 will hardly be bought for a CPU that costs almost $1000 to overclock it, yet our test results suggest that they can cope with any other CPU which generates less heat than our Intel Core i7-3960X Extreme Edition overclocked to 4.25 GHz at 1.35 volts. That's an impressive performance indeed.
The difference between the Katana 4 and TRUE Spirit 90 is small. At the maximum speed of the fan, the peak CPU temperature is the same (79°C) with both coolers. At 2000 RPM the Katana 4 is 3°C better. The gap shrinks to 2°C at 1600 RPM but the TRUE Spirit 90 goes ahead by 1°C at 1400 and 1200 RPM. So, the two coolers are almost identical in terms of performance. When their 92mm fans worked at speeds below 1200 RPM, the coolers couldn't cope with our overclocked six-core CPU.
Compared to the Thermalright TRUE Spirit 120, the Katana 4 and TRUE Spirit 90 cost $8-10 less but the peak CPU temperature is 7-13°C higher with them, depending on the speed of the fans. It's up to you to decide whether the difference in price covers the difference in temperature.
We measured the noise level of our coolers throughout the entire speed range of their fans. Here are the results:
As opposed to the performance tests, the Scythe Katana 4 and Thermalright TRUE Spirit 90 differ considerably in terms of noise level. The Katana 4 remains subjectively comfortable with its 92mm fan rotating at up to 1650 RPM whereas the TRUE Spirit can only be characterized like that at speeds up to 1390 RPM. The Katana 4 becomes quiet at 1420 RPM and lower and the TRUE Spirit 90, at 1010 RPM only.
The Scythe also sounds better than the Thermalright from a subjective standpoint, the Thermalright rattling a little at speeds of 900 to 1450 RPM. Thermalright should have equipped the TRUE Spirit 90 with a better fan unless that was just a defect of our particular sample.
The Scythe Katana 4 and the Thermalright TRUE Spirit 90 proved to be highly efficient, keeping our six-core CPU stable at clock rates up to 4250 MHz. So, each of them is going to be suitable not only for ordinary desktop PCs but even for overclocked configurations unless you are into setting some overclocking records. That’s quite attractive considering their modest dimensions, weight and price. Both products feature broad compatibility and are easy to install. Their availability isn't a problem, either. The TRUE Spirit 90 is smaller but the Katana 4 is better in terms of noisiness. However, either cooler is going to be an excellent affordable solution for any moderately overclocked PC. Inexpensive but good, the Scythe Katana 4 and Thermalright TRUE Spirit 90 are a real bargain.