Test System
CPU	Intel P4 Prescott 3.0E Retail Socket-478
Mainboard	Asus P4C800E-Deluxe (BIOS 18)
Memory	G-Skill DDR600 512MB
Video	eVGA 6800GT (nForce 66.93)
Power Supply	PCPower&Cooling TurboCool 510 Deluxe
Operating System	Windows XP SP2
Water Cooling	Alphacool Xtreme Pro Set AP1500 pump (900 LPH ~ 1500 LPH) 900LPH, Black Ice Xtreme II, 2x12cm Papst 55CFM fans, 6mm tubing.

Besides using Asus Probe to monitor the Prescott's internal thermal diodes, I placed a thermistor from a TTGI Fan Master SF-609 between CPU, and water block as close to the core as possible without affecting contact. Although time consuming, repeating this process several times is the best way to ensure the water block and thermistor are seated properly. Of any water block I've ever used the CAPE due to its minimal footprint, was the easiest thermistor placement I'd ever done. The close-up below reveals final thermistor placement for CPU temp.



I must mention an aspect of Alphacool's Xtreme Pro Set which I find most comforting. As listed in the system spec's the kit features two Papst 4412 F/2GL fans which belie their 26dBA noise-level, operating almost silently. I've placed my system right near my monitor on a table where it's at working level, at first I was running two Sunon 12cm/90CFM fans which at 44dBA gave me a headache in about two seconds. Switching out the Sunons for the Papsts had a negligible impact on system (CPU) temperature, however; the noise difference was substantial. Even using the Fan Master to reduce the Papst RPM from 1600RPM down to 800RPM had a very small impact on temp except when overclocking under LOAD. I only needed to run the fans at 1290RPM to maintain stability during full LOAD, with the CPU overclocked to 3750MHz, and at 1.465Vcore. The photo below shows the setup.



I ran the water block through a series of simple tests basically running the processor under Idle at its default speed/voltage (3000MHz/1.373V respectively) while recording temps, and then under full LOAD. To produce LOAD stressing the processor 100% I ran a combination of Prime95 Torture Test Small FFT's, and SETI concurrently. Running Panopsys freeware utility Throttle Watch 2.0 shows processor usage, and if Thermal Throttling is activated. I repeated these tests, overclocking the processor to 3750MHz (250FSB), at 1.465Vcore, again under Idle and then LOAD. There are four thumbnails below exemplifying each stage of the test. The first thumbnail (left) running Idle at 3000MHz, the second (right) running LOAD at 3000MHz, Vcore remained at 1.375V in each case. Room temps during testing remained between 17_C/62F ~ 19°C/66F.



The next thumbnails lead to screenshots taken running the Prescott overclocked 250FSB speed effectively 3750MHz. To maintain stability under full LOAD (SETI/Prime95) while overclocked required raising Vcore from 1.373V to 1.465V. Once again room temps during tests remained between 17°C/62F ~ 19°C/66F.



Using Hans Chung's freeware program CPU Wattage Calculator we can extrapolate the approximate wattage output of our Prescott 3.0E while overclocked 3750MHz and at 1.465Vcore to be 126.29W. Applying the required data for the C/W aspect of the Calculator we get a C/W rating (during Load) of 0.12669 C/W (indicated below).



The chart below summarizes our data.





Conclusion:

Alphacool continues to manufacture some of the best water blocks on the market to date. The CAPE KC42-X2 is one example of their efforts and a very effective cooling solution. It's compatible to just about any socket type including S775 and S939. Not only has this water block impressed me with its performance I absolutely love the ergonomics.

Perhaps what impressed me most was the moment during system setup when I switched out the Sunon fans I substituted for the Papst fans Alphacool originally provided with the Xtreme Pro Set. The noise level dropped from annoying to completely peaceful, yet the temp levels were basically left unaffected. I realized even when the system was several feet away how loud the Sunons were. I surely underestimated Alphacool's ability to mate the hardware with their water blocks. Although this review focused on the CAPE KC42-X2, I cannot avoid praising the silence of Alphacool's AP1500 which was barely audible. Mated with the Papst fans the system was most refreshing. It tackled one of the hottest running CPU's on the market, and did it without uttering a peep. Sweetness is how I would explain this experience overall. Alphacool's CAPE KC42-X2 can be found at Alphacool store for €37.50.

Questions/Comments: forum thread