Performance
Overclocking an Intel Core i7-4770K with a reference cooler? Then do so at your own peril. At 4.4GHz, out chip soared past the 90ºC mark and generated enough heat for us to have to cancel the benchmark early - there's no use potentially harming a £250 chip just to highlight the inadequacies of reference cooling.
At these speeds/voltages, high-end coolers make a whole lot of sense, and there isn't much between the Zalman LQ135 and Noctua NH-D15. To our own surprise, it's the all-in-one liquid cooler that has the slight edge.
However, the excellent temperature results do come at the expense of noise. Zalman's cooler is comfortably quieter than reference, but it's also noticeably louder than a quality air-cooler such as the NH-D15. With the LQ135 installed, we found pump noise to be bothersome with the system idling - it's clearly audible in an otherwise quiet rig and can be quite distracting. Under load, the up-to 2,000RPM fan masks the noise of the pump but becomes frustratingly vocal in itself.
Is the LQ315 loud enough to put off performance enthusiasts? Not at all, but noise levels are high enough to deter users looking to build a quiet PC. In contrast, the Noctua NH-D15 air cooler can barely be heard at all times.