OCLabs Waterblock Review

This OCLabs PlexyBlock waterblock is designed to fit most processors that use a heatspreader. Here is an overview of the system and testing methodology.

Foxconn 975X7AA-8EKRS2H Intel 975X Express Chipset
Pentium 4 830 (3.0Ghz) 2x1MB L2 cache 800MHz FSB (Dual-Core)
OCLabs PlexyBlock 2-barb
OEM Heatsink
The watercooling system consisted of a Hydor L30 pump, Black Ice Extreme radiator, Sunon 120mm fan (running 12v), and a small reservoir for water storage and air collection. 1/2" I.D. hose was used throughout with minimum hose lengths used whenever possible.

Foxconn Fox One software was used to obtain and record system temperature information and being that this is a dual core processor two programs were used to provide processor usage, Prime95 and AutoGK.

Editors note: Even though the Windows XP task manager reported 100% processor usage we could never attain a 100% of the rated heat output as documented by Intel (see below) when using Prime95 and AutoGK as a basis for that heat production. Knowing this both programs were run together until the maximum temperature was attainted and stabilized.

Other things to consider when judging software induced heat output.
a) Clock throttling by the processor at high temperatures.
b) Normal software isn't designed to produce maximum heat output.
c) Variances of cooling temperature.
d) Variances in CPU load.
e) Inaccuracies in thermal diode readouts.
Of course the list goes on..

Our testing methodology is aimed to provide a real world look into this heatsink given the test system provided.

A C/W rating can quickly be calculated using this formula.

C/W = (CPU temp - Ambient temp)/(Variance(%) * CPU Watts)
Allowed variance for this test = 80%
CPU Watts = 130W

0.13 C/W = (39.5C - 26C)/(.8(130W))

For this next test the FSB was cranked up to 250Mhz and the test was re-run.

To calculate a new C/W rating for this test we will need to factor in the increased processor wattage. The formula and constants for this are listed below.

ocC/W = dCPU Watts * (ocMhz / dMhz) * (ocVcore / dVcore)²
ocMhz = 3750
dMhz = 3000
ocVcore = 1.4
dVcore = 1.3
The variance still applies for our C/W calcuation
Allowed variance for this test = 80%
CPU Watts = W

0.14 C/W = (48C - 26C)/(.8(188.5W))

In our heatsink and waterblock tests we don't really focus on overall load temperatures but rather how well the product can remove heat given a specified heat load. Since this is a real world testing method we need to take into consideration real world variables and estimate tolerances. This is why we normally only apply 80% of the total wattage output to our heat calculations.

The resulting C/W number is used to rate how efficient a heatsink or waterblock is based on the given heat load. These numbers can be used to determine heat capacity, the larger the difference the less efficient the heatsink is. (aka not good for overclocking)

As expected the stock Intel heatsink is not the best solution for any kind of overclocking however the OCLabs plexiblock does a very good job at keeping overall temperatures down and the C/W rating is not only low but pretty much equal between the two tests. Basically this means that the Plexiblock in this system didn't reach a theoretical cooling limit and can still take some abuse. However running a high speed 120mm fan at 12v is not our idea of a good time.

Keep in mind these calculations are provided for demonstration purposes only and may not reflect the actual lab tested C/W rating, but we're pretty close