CPU: Intel i5-2500K
Thermal Paste: Arctic MX-4
Motherboard: ASUS P67 Sabertooth
RAM: 2x4GB PNY Optima DDR3
OS HDD: OCZ Agility 3 60GB SSD
Secondary HDD: Seagate Barracuda 2TB
OS: Windows 7 Professional 64-bit
For the load tests, Prime95 was used to stress the CPU to 100% and then used RealTemp to record the temperatures. Unlike an air cooled unit, the Kühler H2O 620's liquid takes a short while to reach a steady temperature. To that end, the test was allowed run for fifteen minutes before recording the temperatures to make sure the operating temperature of the liquid system had been achieved. Two different conditions of the i5-2500K were tested:, the default settings, and overclocked to 3.8GHz and 1.26V. The single value recorded is the average temperature of the four cores.
Being the smallest liquid cooler we've tested, the 620's performance was about on par with the higher end air coolers we've tested before with heavier thermal loads we see when we begin to overclock. It's small size does have it lagging a little bit for idle and stock conditions, before the thermal capacity of the water has been able to start "stretching its legs" and picking up an advantage over air coolers. Of course, the Kuhler 620 sports a smaller and quieter form factor than it's big brother, the Kuhler 920, and most aftermarket air coolers, for that matter. It should also be noted that our tests were done with relatively conservative ramp ratios for fan speed to keep operation on the quieter side, and if you want it, there's extra cooling capacity available, albeit the noise penalty becomes extreme pretty quickly, as the included fans do become rather loud at higher speeds.