The Skylake-X Mess Explored: Thermal Paste And Runaway Power

Manual Overclocking & Conclusion

The Motherboard Manufacturers’ Duty

Ultimately, we’re looking at power consumption numbers similar to some high-end graphics cards when we start messing with Skylake-X. AMD’s FX-9590X doesn’t even come close to these results, if that means anything to you. This means motherboard manufacturers need to start spending money on better components and cooling solutions to take care of those components. Otherwise, long-term reliability will be hard to guarantee. Ultra-durable and military-class components don't have to be exclusive to top-end products; they can bolster mid-range platforms, too.

Motherboard manufacturers could have and should have known that Intel's Skylake-X CPUs would consume power indiscriminately, in spite of the company's laughably low TDP specifications. Everyone has access to Intel's datasheets, not just us.

Different motherboards will be affected to different degrees by our findings, and the one we tested isn't a flagship model by any means. You shouldn't generalize our results to mean there's an impending VRM-related disaster hanging over the heads of all Skylake-X owners. Boards from every manufacturer across a number of price points need to be tested before such a claim can be made. What we do know is that, although the problem originates under Intel's heat spreader, fault is also found with motherboard manufacturers as well.

We already have a high-end motherboard on its way from the same manufacturer, and we'll report our findings after running the same battery of tests.

Overclocking For Power, Not Frequency

Although we ultimately wanted to explore the CPU's and VRM's cooling problems, we were also curious about Skylake-X's remaining overclocking headroom. Rather than targeting specific clock rates, though, we systematically pushed our Core i9-7900X to 250W and then to 300W. That's all its technical specifications allow for, so that’s where we stopped.

Observation #5: We aren't here to destroy our hardware. Enthusiasts need to decide on their own if they're willing to risk $1000 components. Power users on the overclocking circuit typically have processors provided to them, so a single CPU isn’t something to lose sleep over. We, however, along with most folks only have one sample to work with. Failure would be far more devastating. Technical specifications and limits are there for a reason, and in this case we're honoring them.

Let’s start with the massive 250W, which Intel's Core i7-5960X reached at 4.8 GHz back when we reviewed it. Core i9-7900X gets there at 4.5 GHz under Prime95, and at 4.6 GHz with LuxRender in a console loop. Other applications yield better results, depending on their workloads.

Intel’s Core i9-7820X doesn’t really do any better: it’s separated from the larger 10-core processor by only 20W when performing the same tasks. If you're overclocking this way, pay close attention to wattage and adjust the clock rates and voltages via trial and error, depending on the applications you use.

250W & The Limits Of Normal Water Cooling

In our scenario, we occasionally hit the 270W mark, which probably represents this specific motherboard’s limit. In other words, MSI’s X299 Gaming Pro Carbon AC stays approximately 30W below the maximum wattage allowed by Intel’s technical specifications. The problem is that most custom water-cooling setups aren't able to keep the die and package cool enough to prevent throttling. Even with a water temperature of 30°C, it wasn't possible to run under load for more than 10 to 15 minutes without thermal issues.

The CPU throttles before the motherboard’s VRM has a chance to hit 100°C. This means that all of the flashy plastic parts on top of the VRM are basically useless, since the CPU throttles before they can do anything. Once again, here’s the video to go along with the graph:

Intel’s Limit: 300W & The Mild Scent Of Disaster

Now, can we hit the 300W mark without our system dying a fiery death using our trusty Alphacool Eiszeit 2000 Chiller? To make a long story short: yes, we can...for about 10 minutes. After that, the voltage converters hit 105°C and the CPU’s frequency drops to 1.2 GHz with a power consumption of 70W. That’s enough for the components to recuperate quickly, after which the whole sequence starts over, resulting in an endless loop.

So close, but no cigar. Then again, who else out there uses an Alphacool Eiszeit 2000 Chiller? Most folks won't be able to push their system to the brink of death like this without delidding their processor first. Even with our high-end cooling solution, the Tpackage measurement exceeds 100°C, while the cores run at 94°C and up. This can’t be called sufficient cooling by any stretch of the imagination.

Our video shows the motherboard and its hot-spots once again. In spite of the 105°C you'll see in a few places, none of the components are in danger, since none of the ones that have a temperature limit below this number are affected. That’s at least something.

At least we can rest easy knowing that few power users will ever take their Skylake-X CPUs this far. And if your job involves testing high-end hardware, you shouldn't have a problem locating a suitable motherboard able to handle the heat.

Conclusion

So, what’s the bottom line? Intel is pushing the envelope once again with a factory-overclocked Xeon processor doing double-duty as a high-end desktop masterpiece. We're getting the sense, though, that the revered Core architecture can't be pushed much further. Everything works well enough this time around, at least. And if Intel hadn't chickened out and put thermal paste between its die and heat spreader, there might have been a happier ending for everyone involved in this story.

As it stands, even a custom water-cooling loop has to throw in the towel at 250W, long before most motherboard voltage converters hit their limits. Under normal operating conditions, the CPU, and not the motherboard, always throttles first.

Nevertheless, motherboard manufacturers aren’t blameless when it comes to the issues we encountered at launch and continue battling today. Using more thermodynamic expertise and less flashy plastic pieces would have paved the way for brawnier motherboards at the same price points. This would have ended the speculation before it even started. Anything designed to be just good enough always leaves you with a bad aftertaste, particularly since you never know when you might need a little extra headroom.

[Editor’s Note: We reached out to Intel for commentary back in March after  a number of readers speculated about Intel’s choice of thermal paste on Kaby Lake, and in response to our article De-Lidding And Overclocking Core i7-7700K With Water And LN2. We did not receive any technical or marketing explanations at the time, but we have followed up again related to the Skylake-X issue, and we will update this article if and when we receive a reply.]

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