Performance
Since it’s our first review of the cooling on Skylake-X platform then we do not have any base of results. However, the most important is what you can achieve using the Heatkiller.
In tests will be used the latest Intel i9 7900X processor. After reading early Skylake-X reviews I was a bit surprised how high are the cooling requirements of this processor. When I had a chance to test it myself then I found out what a challenge is to keep it cool.
Even though the i9-7900X TDP is 140W then real wattage is much higher so if you think about any overclocking or even keeping reasonable temperatures at default settings then you need really good cooling.
Our custom water cooling kit contains the Heatkiller CPU and VGA blocks and dual 360mm slim radiators with 120mm 1000RPM fans on one side. Let’s say radiators could be better but their surface is still above average.
Below are results at three settings. CPU has been loaded with AIDA64 CPU and FPU tests. Each test took 30 minutes what is more than enough to stabilize temperatures.
First test has been performed at default/auto settings so about 1.05V CPU voltage. I’ve mentioned that the 7900X processor has 140W TDP but during full load test we have seen about 200W. Data was provided by TP-Link Smart Plug. All that to run all 10 cores up to 4GHz.
Idle temperature is between 24°C and 28°C what is pretty good considering that ambient temperature is about 23°C. Maximum temperature in the first test was 58°C what is also good for a 200W CPU. At these temperatures Intel Turbo Boost was setting CPU between 3600MHz and 4000MHz. Maximum single core frequency is 4500MHz but it’s not possible while all cores are under load.
For the second test voltage as been raised to 1.15V. At this voltage the Smart Plug was showing about 300W only from the CPU. It’s already a lot while voltage is still low.
1.15V seems like a maximum stable and safe voltage for 24/7 work but that’s only because we have high performance cooling which is way above any standard solution. It’s also impressing that all cores can work under full load at 4500MHz.
Maximum temperature of 87°C seems high but that’s full load temperature while most applications can’t make CPU to run so hot. It’s still below the point at which CPU protection and throttling enables so 105°C.
I won’t hide that I’m fully statisfied of stable 4500MHz at still safe temperatures. In various reviews around the web, we can see that there are problems at this frequency while the Heatkiller provides enough heat dissipation to cool down this little devil.
The third test and one more time voltage goes a bit higher. This time it’s 1.20V, what let to run the 7900X at 4.7GHz. Pretty high frequency for the given voltage. Worse looks CPU temperature. The Smart Plug is showing about 350W on the CPU ( about 440W total PC wattage ). So much heat represented in watts focused on a quite small space is really hard to transfer in short time. The Heatkiller does a great job cooling it but it’s still not enough to keep higher overclocked i9-7900X stable and at reasonable temperatures.
I’m still surprised that our CPU was able to run stable at these settings even though maximum temperature was reaching 102°C. Of course it’s not safe for the CPU and for sure long work like that will shorten its life. At the same time our tests prove high performance of the Heatkiller water block.
Below is a graph showing how temperature is growing at higher wattage. Looks like efficiency of cooling is pretty good what we wouldn’t see looking only at the maximum temperatures.
At the end three more photos of the test rig as there is never enough of photos.
