Power Consumption and Overclocking
As expected the new 8-core models are serious power pigs. The 9700K matched the 7820X with a system draw of 235 watts when running our HandBrake workload. The 9900K pushed consumption 9% higher hitting 255 watts which is 13% more power than the 16-core Threadripper 2950X system consumed.
We find a similar story when testing with Blender though the AMD CPUs did perform better in this application and as a result the 2950X was able to work a bit harder, but even so it still consume less power than the 9900K. That’s enough power consumption data for the moment, let’s check out overclocking performance.
Overclocking these 8-core parts to 5.1 GHz wasn’t easy, it required 1.375v and a massive liquid cooler, you aren’t hitting this frequency with a 240mm closed loop cooler, 5 GHz is probably off the table as well, but we will talk about thermal performance soon.
Looking at the multi-threaded results the 9900K saw an 8% performance boost while the 9700K saw a 7% boost. I should also note that I have two 9900K samples and both struggled with the 5.1 GHz overclock. They could boot into Windows at 5.2 GHz and run a few basic tests but anything more would result in the blue screen of death, even at 1.45v.
Moving on to Corona the 9900K was 7% faster once overclocked while the 9700K enjoyed a 9% performance bump.
Finally we have the Premiere results and again the 9700K saw a 9% performance boost and the 9900K an 8% boost. So only single digit gains making it hard to justify the increased power consumption and operating temperatures.
Speaking of power the 9700K configuration consumed 15% more power once overclocked and the 9900K an additional 19% taking the total system consumption to 294 watts.
When it comes to operating temperatures I have nothing but bad news. these 8-core CPUs might have a STIM pack, I mean soldered thermal interface, but you wouldn’t necessarily know it. Stock out of the box with either a premium air-cooler or a recent closed-loop liquid cooler you’re look at load temps well into the 80’s and overclocking is basically out of the question. Sure 5 GHz might be okay for games but if you’re placing all 8-cores under prolonged stress temperatures will hit 100c, and I was testing in a relatively cool room inside a well ventilated case.
Using a custom liquid cooling setup only reduced the stock operating temperature by 8 degrees and we’re talking about a $400 - $500 kit here.
It was possible to run at up to 5.1 GHz but even then temperatures were stick knocking on the door of 100 degrees which is obviously insane. So the 9900K might be fast but good luck keeping it at a reasonable temperature. We ran out of time to test thermal performance of the 9700K, but we'll include that data in future content, for now let’s move onto games.