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

Living On The Edge (At Stock Settings)

Default Settings, Cheats & Heat

The first criticism, which we heard long before the launch, came from the direction of motherboard manufacturers. Typically, they'd take a normal closed-loop liquid cooler (they're scattered across the labs of these companies), slap it on top of a Core i9-7900X, and develop a BIOS that satisfies Intel's requirements and makes the board look good compared to its competition.

It didn't go down that way this time, though, and it sounds like Intel's rushed launch was to blame. None of the motherboards we tested ahead of the embargo behaved well. They all deviated from Intel's specifications in some way, from faulty P-states, incorrect Turbo Boost frequencies, and so much more.

But what struck us as most surprising was that every manufacturer had a skeleton in the closet. Let's compare the Asus Prime X299-Deluxe and MSI's X299 Gaming Pro Carbon AC (based on Thomas Soderstrom's testing). While Asus hits the brakes at stock settings, MSI leaves the power running full-tilt. Suddenly, the waste heat we were seeing makes a lot more sense.

Since Prime95 does not output any results, you need to be a bit more critical about where the differences in power consumption come from. To start, MSI has a BIOS entry called Enhanced Turbo, which is set to <Auto> by default, meaning it's active. In order to find (and disable) it, you have to open the Advanced BIOS menu and activate the Expert mode. Turbo Boost normally allows two cores to hit 4.3 GHz in lightly-threaded tasks, but with this switch in its default position, all cores are automatically pushed to 4.3 GHz under load. This is a nice factory overclock, which is of course stabilized by an automatic voltage adjustment.

At 4 GHz with Enhanced Turbo turned off, our CPU sucks down an astonishing 230W. The 4.3 GHz setting imposed by Enhanced Turbo mode looks a lot more conservative in comparison at 160W (with peaks just over 230W) under Prime95, curiously enough. This can be explained when you see Enhanced Turbo mode pulling clock rates back more sharply in AVX-heavy workloads.

Rendering with Cinebench, which doesn't utilize AVX instructions, changes this picture dramatically. The 4 GHz configuration consumes 145W for a score of 2169, while every core running at 4.3 GHz via "Enhanced Turbo" hits 190W for a modest jump to 2312 points. That's worrisome. You get a 6.6% performance benefit from 7.5%-higher clock rates at a cost of 31% more power consumption. Talk about a poor bang for your power/heat/cooling buck.

Checking VRM Temperatures

Let's get back to the voltage converters and test how our motherboard holds up under full load in the Core i9-7900X's default state, without any manual overclocking.

The two scenarios above presented us with a continuous load of 160W (slightly higher than Intel's rated TDP) and a direr 230W reading. That was the maximum we could generate using factory settings and our most demanding software. It's a worst-case scenario, to be sure.

Our comparison includes sensor data and an infrared-based analysis of thermal changes over 20 minutes.

Entry-Level: 160W+

According to our chart and video, the Core i9 is still in good shape thermally. A lot of that is owed to our high-end cooler. We also see that the package itself is already hotter than the maximum core temperatures. Testing with a compact all-in-one liquid cooling system yielded acceptable results still, but air cooling resulted in throttled clock rates after only a few minutes.

In places, the graph reveals consumption spikes up to ~230W. The CPU regulates the power requirement as it sees fit in order to prevent performance issues, though.

The motherboard's voltage converters handle this task easily; there is no reason to worry:

Intel Core i9-7900X Heating Up with 160 Watts on Vccin

Ramping Up To 230W

Peak power consumption without overclocking reaches as high as 230W when we turn Enhanced Turbo mode off. The performance curve is much smoother, but our thermal readings are all much hotter. This applies to the voltage converters too, which work a lot harder under an almost constant load.

The motherboard's VRM is scratching at 90°C, but there's still a little headroom left. So long as we don't increase clock rates or voltages, we remain within our hardware's tolerances. It's just a little unsettling to be within 15°C or less of a VRM throttling event before any overclocking at all.

Intel Core i9-7900X Heating Up with 230 Watts on Vccin

When it comes to gaming, the Core i9-7900X lands well under 100W. All that tells us, though, is that Skylake-X is useless for gaming-only. Graphics-bound titles simply do not utilize this chip's host processing resources fully.

Observation #4: Depending on whether you use the Enhanced Turbo option or not, power consumption in excess of 230W (in AVX-heavy workloads) or as high as 200W (without AVX) is possible right out of the box. That's no longer in the realm of air cooling. You need a good closed-loop liquid cooler at minimum. Even that's going to hit its limit, though, since the core temperatures peak at close to the point where thermal throttling begins.

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  • You guys don't get it??? I talked to some people who got 6 core of Skylake-X and they were able to push CPU up to 4.6Ghz on all cores where temperatures were fine under Prime. Again temperatures were much lower in anything else. In my opinion Prime is rather unrealistic stress test, not to say useless crap proving nothing. I am not defending Intel but you all approached this problem with a wrong assumption.

    With 7900X which is still built using 14nm fabrication process, there is no in hell you are going to be fine with temperatures on overclocked 10/20 cores. That's just too many of them to keep them cool.

    If someone gets 10/20 CPU i would not push more than 4Ghz. That is a max realistic clock speed for such CPU, with 8 Core you will be better but i'd say the best thing to buy is actually 6/12 Core which can easily run at @4.5Ghz.

    People don't play Prime or any other similar >Mod edit: keep it clean<test. People game, do programming, stuff where you will never see CPU showing overheating issue. And again keep 10/20 at 4.0Ghz max. Honestly you won't gain a thing running at 4.4Ghz.
  • Also i might want to add is to wait for second iteration of x299 boards. The first batch is a joke from cooling point of view. Evga is one of the companies which will get it right. X299 need copper based cooling for VRM and chipset and also 2x8pin CPU connectors with recommended PSU of 1000W+. That's how i would run x299 setup.
  • AgentLozen
    Freak777Power said:
    You guys don't get it??? I talked to some people who got 6 core of Skylake-X and they were able to push CPU up to 4.6Ghz on all cores where temperatures were fine under Prime. Again temperatures were much lower in anything else. In my opinion Prime is rather unrealistic stress test, not to say useless crap proving nothing. I am not defending Intel but you all approached this problem with a wrong assumption.


    What's wrong with using Prime? It does a good job of testing the thermal limits of a CPU. You wouldn't test the limits of a weight lifters strength with 5 pound dumb bells. You need to go all out.

    You say that the author of this article approached this problem with a wrong assumption. Do you think that there's nothing noteworthy of Skylake X's thermal performance?

    I think this article did a good job of pointing out the glaring flaws of Skylake X. The conclusion is really interesting: "We're getting the sense, though, that the revered Core architecture can't be pushed much further." That gives me chills. I never thought I'd see the day when Core hit its limits.
  • rothbardian
    496490 said:
    The conclusion is really interesting: "We're getting the sense, though, that the revered Core architecture can't be pushed much further." That gives me chills. I never thought I'd see the day when Core hit its limits.


    It's a chilling conclusion indeed. It all points out to AMD's multi-die, multi-ccx architecture of Ryzen Threadripper being supperior to Inte's Core on all counts.
  • Wisecracker
    Good job -- Thank you for the in-depth analysis.

    BUT (you knew that was coming ;) right?), I question the need to call-out motherboard OEMs. I agree with the comments regarding unnecessary 'Bling' but they clearly feel they are delivering what the market demands in that regard ...

    It seems off-kilter to focus/blame board components and OEMs at the top of your conclusion page, and not really Chipzilla, while noting Sky(lake-X)-rocketing heat/power beyond that of the previous-gen 32nm AMD FX-9590 (constantly derided since its introduction as a power-hungry 'heater').

    Know what I mean, Vern?

    edit: How could I have misquoted Earnest!
  • FormatC
    To be honest, this was translated in absolute hurry over the weekend and sounds now (without my lyrics) a bit harsh. But one thing is fact: without all this kiddish plastic crap, covering the cooler surface, it might work a lot better. As I wrote on page One (intro); it is a causal chain and at the begin is the CPU.
  • AgentLozen
    Quote:
    See what I mean, Vern?


    I know its petty, but isn't the line, "Know what I mean?" We're talking Jim Varney, right? Haha.
  • JamesSneed
    This article spells out the points why I decided to build a Ryzen based system. I waited for Skylake-x and the thermals / power are just way to off the charts for the little extra performance. I could not be happier with the Ryzen 1800x build and yes I know I paid more for something you can get in the 1700 and OC it. I certainly agree anyone needing more than 8-cores should wait on Threadripper as it really has a chance to take Intel on performance due to these very same thermal / power issues in the i9 which means the higher core counts won't hit the same frequencies.
  • JamesSneed
    482859 said:
    To be honest, this was translated in absolute hurry over the weekend and sounds now (without my lyrics) a bit harsh. But one thing is fact: without all this kiddish plastic crap, covering the cooler surface, it might work a lot better. As I wrote on page One (intro); it is a causal chain and at the begin is the CPU.


    I agree, they should be called out when form causes a hit to function. I didn't find it harsh at all. Motherboard makers are all enamored right now with shiny pretty and are loosing sight on quality. I don't care if it has LED's or looks "cool" but never should that be at the expense of the motherboards main function.
  • mrjhh
    Power consumption and TDP are only marginally linked. Maximum power consumption relates to the maximum the chip could possibly use, while TDP is what a heat sink needs to be able to dissipate. The chip will thermally throttle if the maximum power consumption extends for long, but this condition should not happen in normal usage. But, if one uses all execution units within the processor at the same time, one will hit maximum power consumption at least momentarily. But, it's hard to keep all execution units running all the time, as there are typically cache misses which slow the processor, as well as software inefficiencies preventing running all execution units all of the time. Normally, that would put the average power consumption within TDP limits. Unusual use cases could exceed TDP, and cause thermal throttling.
  • 496490 said:
    Freak777Power said:
    You guys don't get it??? I talked to some people who got 6 core of Skylake-X and they were able to push CPU up to 4.6Ghz on all cores where temperatures were fine under Prime. Again temperatures were much lower in anything else. In my opinion Prime is rather unrealistic stress test, not to say useless crap proving nothing. I am not defending Intel but you all approached this problem with a wrong assumption.
    What's wrong with using Prime? It does a good job of testing the thermal limits of a CPU. You wouldn't test the limits of a weight lifters strength with 5 pound dumb bells. You need to go all out. You say that the author of this article approached this problem with a wrong assumption. Do you think that there's nothing noteworthy of Skylake X's thermal performance? I think this article did a good job of pointing out the glaring flaws of Skylake X. The conclusion is really interesting: "We're getting the sense, though, that the revered Core architecture can't be pushed much further." That gives me chills. I never thought I'd see the day when Core hit its limits.


    Because it is unrealistic, and finding thermal limit is just pointless. Go and read Intel specs sheet and tells you about this processor thermal limit. We really don't need any test to show such thing. Tomshardware spent pages of writing something pretty much everyone knew about if you were to read Intel specs. And even if you did not logically anyone can conclude that using same 14nm fabrication process won't play in favor in term of overclocking and heat.

    Again 10/20 is a lot of cores and to cool that with 4.0 Ghz+ clock speed, good luck with that.

    You people think that AMD Thread Ripper will run cooler, it will with 2.4Ghz clock speed. Seriously i had chance to play with every iteration of Xeon and AMD counter part CPU and you people have no idea of what you are talking about. 18 Core Broadwell-E or Haswell-E CPU for example is hell of task to cool down therefore those CPU run <3.0Ghz speed. We didn't hit any limit with Core CPU, but with what's possible using 14nm fabrication process. The fact that you can even overclock 10/20 to 4.4Ghz with such core count and complexity CPU package itself carries is AMAZING compared to AMD Ryzen which can't hit anything above 4.0Ghz with rather high temperature.

    You people get your fact straight.
  • FormatC
    If you read the intro between the lines, this test is a kind of answer to a YT video that was telling us, that all motherboard makers failed. I only tried to show, that we have headroom enough, to use this CPU as is without any kind of limitations. Only manually OC is able to bring it in trouble. :)
  • kinggremlin
    Prime 95 is the cpu equivalent of furmark. It's basically a power virus that does not represent the power usage of any other program you can come up with including other stress test programs. Intel implemented automatic throttling for their igpu's when furmark was detected. I wouldn't be surprised to see the same thing for prime95 on their cpu's.

    The bodybuilder analogy is idiotic. The prime95 equivalent would be to require grocery stockers to bench 500lbs as part of the hiring process to demonstrate the strength necessary to lift grocery products on the shelf. They will NEVER have to lift that much making it a meaningless and unrealistic test.
  • Phil_52
    Would love to hear the reviewers thoughts on how to setup these boards to de-clock the CPU in a way that reduced the head issues without too much damage to normal performance. I have just ordered a X299 setup and am more interested in the chipset features (PCI Lanes, Multi M.2 support etc) than the RAW horse power of the CPU.. So the question is, if I do the opposite of nature and under-clock... can I get a good balance ?
  • FormatC
    Simply use the mainboards functions to limit the wattage and / or play with Vcore and Vccin. I will also write a follow-up in both directions when I get a better mainboard.
  • bloodroses
    2070440 said:
    496490 said:
    The conclusion is really interesting: "We're getting the sense, though, that the revered Core architecture can't be pushed much further." That gives me chills. I never thought I'd see the day when Core hit its limits.
    It's a chilling conclusion indeed. It all points out to AMD's multi-die, multi-ccx architecture of Ryzen Threadripper being supperior to Inte's Core on all counts.


    Once/If Threadripper is able to clock higher and have a faster IPC, then AMD can talk about being superior. Looking at the leaked specs so far, neither appears to be true. While it's great that AMD is back in the game again and finally giving Intel competition, they are no means superior outside cost/value and core count.

    To give a comparison, Threadripper supposedly will have a tdp of 125-155w, with the highest topping out at 4.1ghz boost. The 10 core equivalent has a 125w and 4ghz boost.

    http://wccftech.com/amd-threadripper-1998x-and-threadripper-1998-processors-x399-x390/

    Chances are these will run quite hot as well and are huge in size. These 2 links show the size of the die and coolers needed:

    https://www.lowyat.net/2017/133239/computex-2017-noctuas-amd-threadripper-cpu-cooler-massive/

    http://www.pcgamer.com/amds-threadripper-is-huge-with-an-equally-large-socket-and-cooler/


    Intel's I9-7900x has a tdp of 140w, with a 4.3ghz boost. Their die size is still roughly the same as that of the rest of their core lineup in comparison to Threadripper's monstrous size. The biggest mistakes Intel made was the thermal paste (as the author mentioned) and while not really a mistake; trying to cram too much into a tiny space for their socket.
  • JamesSneed
    1069610 said:
    2070440 said:
    496490 said:
    The conclusion is really interesting: "We're getting the sense, though, that the revered Core architecture can't be pushed much further." That gives me chills. I never thought I'd see the day when Core hit its limits.
    It's a chilling conclusion indeed. It all points out to AMD's multi-die, multi-ccx architecture of Ryzen Threadripper being supperior to Inte's Core on all counts.
    Once/If Threadripper is able to clock higher and have a faster IPC, then AMD can talk about being superior. Looking at the leaked specs so far, neither appears to be true. While it's great that AMD is back in the game again and finally giving Intel competition, they are no means superior outside cost/value and core count. To give a comparison, Threadripper supposedly will have a tdp of 125-155w, with the highest topping out at 4.1ghz boost. The 10 core equivalent has a 125w and 4ghz boost. http://wccftech.com/amd-threadripper-1998x-and-threadripper-1998-processors-x399-x390/ Chances are these will run quite hot as well and are huge in size. These 2 links show the size of the die and coolers needed: https://www.lowyat.net/2017/133239/computex-2017-noctuas-amd-threadripper-cpu-cooler-massive/ http://www.pcgamer.com/amds-threadripper-is-huge-with-an-equally-large-socket-and-cooler/ Intel's I9-7900x has a tdp of 140w, with a 4.3ghz boost. Their die size is still roughly the same as that of the rest of their core lineup in comparison to Threadripper's monstrous size. The biggest mistakes Intel made was the thermal paste (as the author mentioned) and while not really a mistake; trying to cram too much into a tiny space for their socket.


    We will see soon enough on Threadripper. I really don't think they will run hot as you do. They have a large heat spreader with the dies underneath spaced out and should be soldered. This should make for lovely cooling capabilities even with air. The 16+ core parts of AMD and Intel are where it gets really interesting seeing how Intel deals with the heat of a CPU that is 60-80% more cores than the 7900x.
  • nyannyan
    Heat is going to be a real problem when the 18 core SKUs come out regardless of Prime95. There are other AVX heavy use cases you know and the headroom will decrease with each additional core. Right now I'm quite satisfied that I went with Broadwell.
  • Aspiring techie
    I can only imagine what will be needed to cool the 18 core variant...
  • techy1966
    Great Article Thank you I found it very interesting and it answered a lot fo questions for me. I think both Intel and the main board makers are at fault. Intel because they rushed these CPU's out and used thermo paste instead of soldered heat spreaders. I also think they have reached the limit of their 14nm process and need to shrink it again.

    Main board makers at fault for as you stated putting all that plastic bling bling on the boards because they think consumers think it is cool. Only teens and 20 something find that cool the rest of us just want fully working boards that do as advertised out of the box. If the plastic bling bling & RGB lighting effects the board performance it needs to go simple as that.
  • the nerd 389
    For your motherboard reviews with this CPU, might I suggest that you look up the rated lifetime of the PWM caps?

    If those are 5k caps, they'll only last 5000 hours at their rated temperature. Lifetime usually doubles for each 10C under that rating.

    These CPUs often end up in entry level workstations. If the intended usage pushes the caps to 75 C, and they are the more common 5k/105C, then conventional wisdom indicates that 10% of the caps should fail by the 40,000 hour mark. In those cases where the CPU is fully loaded most of the time, this will occur 4.5 to 5 years of age. This means that there isn't much room for mistakes in the motherboard layout, case design, or airflow requirements. It's something that potential consumers should take into account if they want to get the most out of this platform.

    I'd have to check in more detail to give any estimates for the MOSFET lifetime, but that's another factor to account for if longevity is a priority.
  • chaosmassive
    well done Intel, I applaud you !
  • FormatC
    983009 said:
    For your motherboard reviews with this CPU, might I suggest that you look up the rated lifetime of the PWM caps? If those are 5k caps, they'll only last 5000 hours at their rated temperature. Lifetime usually doubles for each 10C under that rating.
    Suggest it Thomas, he makes the mainboard reviews here. The idea is not bad to see deeper into the tech. I'm testing here VGA boards and I disassemble all.
  • Nintendork
    Intel repeated the P4 Prescott mistakes, they never wanted more than 10 cores for HEDT, not with Zen blowing them in performance per watt, power consumption and temps they forced their HEDT out of reasonable limitis to look good on benchmarks.

    Overaggressive turbo clocks, high power consumption, unacceptable temps, and this is only the 10core...

    Since they dropped the price more than they wanted now they cheap out $1 from solder to toothpaste.