To give the Apex Ultima a thorough workout we installed its components inside in our LGA1366 Core i7 thermal test rig. This comprises a Core i7-965 Extreme Edition overclocked to 3.6GHz with a vCore of 1.3V - the absolute maximum overclock and overvolt the reference Intel cooler can cope with. This is the same test rig we use for all Core i7 coolers, so you can compare the results with the other products we've tested recently. The other components in the test rig include an MSI Eclipse motherboard, Zotac GeForce GTX 280, all housed inside a Cooler Master Stacker 830 chassis.
With all the components installed, the system filled, leak tested and then left to bleed for approximately 30 minutes we loaded up all eight execution units of the CPU with the small FFT test in Prime95. While Prime95 was running we used CoreTemp to monitor the temperature of the CPU, recording the highest temperature of the hottest execution unit. Comparing this to the ambient temperature of our test lab we calculated the results you can see graphed below, shown as the delta T between CPU and ambient temperature. To put these figures into context we've also graphed the delta T values of several Core i7 air coolers we've tested recently.
Swiftech H2O-220 Apex Ultima (12V fans)
Swiftech H2O-220 Apex Ultima (7V fans)
Swiftech H2O-220 Apex Ultima (5V fans)
Titan Fenrir TTC-NK85TZ (max speed fan)
Thermalright Ultra 120 eXtreme 1366 RT
Titan Fenrir TTC-NK85TZ (min speed fan)
Intel Stock HSF
As you can see, unsurprisingly the Apex Ultima performed best with the fans running at 12V. However, at this speed the fans are pretty noisy - so unless you're trying to get the best possible overclock and don't mind PC noise we wouldn't recommend this setting. Dropping the fans speed to 7V dramatically cut the noise they make and the CPU ran barely any hotter. At this speed the delta T of the Apex Ultima is not only far less than any Core i7 air cooler we've tested - it's also considerably quieter. What's more, even after running Prime95 for several hours the radiator was barely warm to the touch, so clearly there was plenty of spare cooling capacity in the loop for adding additional waterblocks, such as a GPU block.
Even with the fans barely spinning while being fed 5V, the Apex Ultima's delta T is still superior to any Core i7 air cooler. However, due to the noticeably warmer (but not hot) radiator you probably won't be able to add any other waterblocks to the loop with the fans spinning this slowly. The idle CPU temperature hardly varied regardless what speed the fans were running at, although it was still much cooler than when fitted with any of the air coolers.