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Intel Core i9-7900X X-Series Skylake-X CPU Review (Page 8)

By: Steven Bassiri from Jun 19, 2017 @ 8:01 CDT
TweakTown Rating: 92%Manufacturer: Intel

CPU Overclocking


I was able to get a nice 4.6GHz on all cores, but of course, you might do better. I would say almost all CPUs can do 4.5GHz on all cores, and even then, the CPU is a monster. I just ran quick CINEBENCH runs; I will do more overclocking investigation when I have more time, as I have only had the sample for a few weeks and had to re-run tests with every new BIOS (more times than I can count).

Overclocking memory on this platform is very easy, the IMC is very well tuned, and it seems that 3200MHz isn't the maximum any longer. Many motherboard vendors have been touting memory speeds over 4GHz, so we should see 3600MHz+ become the standard soon.

CPU core overclocking is a bit trickier because of the massive amounts of heat. A Corsair H100i will let you pump only around 1.25-1.27v before you thermal throttle, so better cooling helps. Even so, I was able to get to 4.6GHz without thermal throttling but to be honest; sometimes it doesn't hurt performance that much as you will see below. I would try and keep temperatures below 80C, but I guess with this processor we are aiming for 90C.


By decreasing the input voltage, I was able to shave a few degrees off one of the cores, so that only three had any type of thermal even at 4.7GHz. The reason that decreasing the ratio between the VCore and input voltage lowers temperatures is because it helps the efficiency of the input VR. Although there are thermal events in both of these scores, they are both higher (although the one with three events rather than four scores better) than the 4.6GHz score.

I believe that on this platform, it will be easier to scale the cores and peg a few high and the rest lower in a step-wise fashion.

Power Consumption


Our numbers were quite shocking to be honest, especially since the CPU isn't overclocked. They say that CPU interconnects take up about 15-30% of the power budget, and it seems that the mesh did add some power consumption.

We also have an integrated VRM and higher clocks to contend with. The integrated VRM lowers the efficiency of the power conversion, so instead of it all being external of the CPU and on the motherboard, it is now shared in two different stages, putting less strain on each stage but decreasing overall power conversion efficiency.

Our results of the CPU power consumption are measured at the 8-pin power connectors, and in this case both, so we went through both levels, and actual power consumption for TDP ratings is obviously going to be a bit lower.

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