We were impressed with the speed of Intel's new Skylake-X chips when we tested them last week. However, the thermals were a major disappointment as the Core i9-7900X was too hot even in combination with a premium all-in-one liquid cooler. Given these findings, we felt that the beast with 10 cores and 20 threads deserves an article about overclocking.
There are two reasons why Skylake-X thermal was bad. Primarily, and probably primarily, Intel believes that they can still make their customers cheaper by using a thermal waste interface material instead of soldering their chips like AMD – I'll go into that later. Another reason why the 7900X reaches boiling temperatures is its extreme power requirements, especially when the unlocked chip has been overclocked.
After unpacking, it had no problem increasing system consumption to well over 200 watts, reaching 260 watts in Cinebench, while AMD's Ryzen 7 1800X had a maximum output of 196 watts. Overclocked, the consumption was almost extreme and reached 402 watts at 4.6 GHz with only 1.2 volts under load.
I should note that CPU-Z does not correctly report the voltages for the 7900X on my Asrock card (it does not report the FIVR or the fully integrated voltage regulator). To display the correct live voltages, I use HWInfo (also known as hardware info).
For those using something like Corsair's Hydro series H100i V2 Extreme, it's simply not possible to prevent the 7900X from throttling at that frequency. As soon as the CPU was put under load, the temperatures rose to 90 degrees and continued to rise from there before the chip finally started to throttle.
However, the resulting performance was impressive. A 10-core / 20-thread chip that runs all the cores at 4.6 GHz is insane, and if you can keep the temperatures low, I see no reason why 4.7 GHz or even 4.8 GHz doesn't possible are.
Hoping to do just that, I built a new test bench with an improved cooling solution thanks to the Pacific RL360 liquid cooling kit from Thermaltake.
This kit costs $ 380 and includes a 360mm cooler 64mm thick. So it's a big boy. You also get a Pacific PR22-D5 pump with a maximum flow rate of 1135 l / h and of course three 120 mm fans. I was interested to see how much this would help and whether it would be enough to keep the overclocked 7900X at bay.
The set-up is rounded off by PrimaChills practice WetBench, with the kind permission of the employees of PLE Computers.
Before moving on to testing, I should mention that it's winter in Australia, so my room temperature was ~ 19-20 degrees Celsius, which is a few degrees cooler than normal. Once the system was warmed up, the idle temperatures were only 26 degrees, but the load temperatures are obviously the real problem.
In the past I could only stabilize the 7900X at 4.6 GHz, but with the improved cooler I managed 4.7 GHz and 4.8 even seemed to be possible with a bit more voltage tuning. At 4.7 GHz, the CPU rose to 60 degrees as soon as it was put under load – much better than the previously seen 87 degrees.
I expected the temperatures to continue to rise quickly, but to my surprise, they didn't, at least not to the extent that I expected. It wasn't long before we were in the mid-1960s, then 70 degrees, but soon the system reached a maximum of 73 degrees and occasionally peaked at 74 degrees for a second before returning to 73 degrees.
With temperatures staying within acceptable parameters, there was no risk of throttling, and Thermaltake's 120mm fans even stayed quiet. As a result, power consumption was also reduced by 7% from 402 watts previously at 4.6 GHz with the AIO liquid cooler to 375 watts. Granted, that still makes the 7900X super hungry for performance, but it's a better result for a 10-core CPU with all cores running at 4.7 GHz.
Overclocking increased the Cinebench R15 multi-thread score by 15% and scored an impressive 2521 points.
Again, there is a 15% increase in performance, this time when testing with 7-Zip, since the 7900X manages 67747 MIPS at 4.7 GHz when decompressing.
The Blender workload was completed in just 14.5 seconds, previously the test took 17.9 seconds, which is a 19% time saving.
The Corona test was completed in as fast as 82 seconds, compared to 97 seconds before, which is 15% faster rendering time.
Don't blink! Our Excel test was completed in just 1.69 seconds, or almost half the time it took for a 7700K bearing.
Wrap things up
With the right cooling solution, the Core i9-7900X can actually be tamed and the results are pretty spectacular. Granted, the power consumption is still hideous, but this is also a 10-core / 20-thread CPU with 4.7 GHz.
The main sticking point of course remains the price of $ 1,000 for the chip, which is a difficult sale for a desktop processor. Realistically, you should spend at least $ 300 on the motherboard and then about as much on cooling again, which makes this package a package of $ 1,600.
It will be interesting to see what Threadripper and its core components will cost for a similar level of performance.
Many have argued that you can only delide the 7900X to lower the load temperatures by at least 20 degrees, but I think you don't have to delid your CPU to get the most out of it, especially if you are such an expensive enthusiast have -grad CPU.
Needless to say, I will not ship Core X CPUs. I think the mod is fun for deep pocket enthusiasts, but most users would rather not risk that expensive CPU and void their warranty in the name of overclocking.
I delivered one of my 7700K chips back in February after suffering terrible heat from overclocking that lowered the load temperature by a full 20 degrees.
At the time, I was disappointed that Intel was selling its unlocked chips with the same thermal interface material as its locked models, and even more annoying that I had to buy a delid tool and a fluid pro connection – essentially $ 40, to own an unlocked core i7, not to mention the need for an improved cooler. My opinion on this topic has not changed.
Those who try to overclock the Core i9-7900X can expect it to land somewhere between 4.6 and 4.8 GHz, depending on how lucky you are with the chip and how good your cooling is (it is better if you are powerful).
Whatever it's worth, Thermaltake's Pacific RL360 liquid cooling kit generated acceptable temperatures when overclocking the i9-7900X, while installing a premium AIO loop like the Corsair H100i v2 causes the chip to be throttled.
As mentioned in our Core X reporting, we recommend waiting for Threadripper to arrive before making major processor purchases. If you've chosen the 7900X with 10 cores / 20 threads, you should be ready to invest in a custom liquid cooling solution if you want to overclock.