Power Consumption

The nature of reporting processor power consumption has become, in part, a dystopian nightmare. Historically the peak power consumption of a processor, as purchased, is given by its Thermal Design Power (TDP, or PL1). For many markets, such as embedded processors, that value of TDP still signifies the peak power consumption. For the processors we test at AnandTech, either desktop, notebook, or enterprise, this is not always the case.

Modern high performance processors implement a feature called Turbo. This allows, usually for a limited time, a processor to go beyond its rated frequency. Exactly how far the processor goes depends on a few factors, such as the Turbo Power Limit (PL2), whether the peak frequency is hard coded, the thermals, and the power delivery. Turbo can sometimes be very aggressive, allowing power values 2.5x above the rated TDP.

AMD and Intel have different definitions for TDP, but are broadly speaking applied the same. The difference comes to turbo modes, turbo limits, turbo budgets, and how the processors manage that power balance. These topics are 10000-12000 word articles in their own right, and we’ve got a few articles worth reading on the topic.

In simple terms, processor manufacturers only ever guarantee two values which are tied together - when all cores are running at base frequency, the processor should be running at or below the TDP rating. All turbo modes and power modes above that are not covered by warranty. Intel kind of screwed this up with the Tiger Lake launch in September 2020, by refusing to define a TDP rating for its new processors, instead going for a range. Obfuscation like this is a frustrating endeavor for press and end-users alike.

However, for our tests in this review, we measure the power consumption of the processor in a variety of different scenarios. These include full workflows, real-world image-model construction, and others as appropriate. These tests are done as comparative models. We also note the peak power recorded in any of our tests.

I’m here plotting the 10900K against the 10850K as we load the threads with AIDA’s stress test. Peak values are being reported.

On the front page, I stated that one of the metrics on where those quality lines were drawn, aside from frequency, is power and voltage response. Moving the needle for binning by 100 MHz is relatively easy, but binning for power is more difficult beast to control. Our tests show that for any full-threaded workload, despite being a lower frequency than the 10900K, our 10850K actually uses more power. At the extreme, this is +15-20W more, or up to 2 W per core, showcasing just how strict the metrics on the 10900K had to be (and perhaps why Intel has had difficulty manufacturing enough). However, one could argue that it was Intel’s decision to draw the line that aggressive.

In more lightly threaded workloads, the 10850K actually seems to use less power, which might indicate that this could be a current density issue being the prime factor in binning.

For a real workload, we’re using our Agisoft Photoscan benchmark. This test has a number of different areas that involve single thread, multi-thread, or memory limited algorithms.

At first glance, it looks as if the Core i9-10850K consumes more power at any loading, but it is worth noting the power levels in the 80-100% region of the test, when we dip below 50 W. This is when we’re likely using 1 or 2 threads, and the power of the Core i9-10900K is much higher as a percentage here, likely because of the 5300 MHz setting.

After getting these results, it caused me to look more at the data underneath. In terms of power per core, when testing POV-Ray at full load the difference is about a watt per core or just under. What surprised me more was the frequency response as well as the core loading temperature.

Starting with the 10900K:

In the initial loading, we get 5300 MHz and temperatures up into the 85-90ºC bracket. It’s worth noting that at these temperatures the CPU shouldn’t be in Thermal Velocity Boost, which should have a hard ceiling of 70ºC, but most modern motherboards will ignore that ‘Intel recommendation’. Also, when we look at watts per core, on the 10900K we’re looking at 26 W on a single core, just to get 5300 MHz, so no wonder it drops down to 15-19W per core very quickly.

The processor runs down to 5000 MHz at 3 cores loaded, sitting at 81ºC. Then as we go beyond three cores, the frequency dips only slightly, and the temperature of the whole package increases steadily up and up, until quite toasty 98ºC. This is even with our 2 kg copper cooler, indicating that at this point it’s more about thermal transfer inside the silicon itself rather than radiating away from the cooler.

When we do the same comparison for the Core i9-10850K however, the results are a bit more alarming.

This graph comes in two phases.

The first phase is the light loading, and because we’re not grasping for 5300 MHz, the temperature doesn’t go into the 90ºC segment at light loading like the 10900K does. The frequency profile is a bit more stair shaped than the 10900K, but as we ramp up the cores, even at a lower frequency, the power and the thermals increase. At full loading, with the same cooler and the same benchmarks in the same board, we’re seeing reports of 102ºC all-package temperature. The cooler is warm, but not excessively so, again showcasing that this is more an issue for thermal migration inside the silicon rather than cooling capacity.

To a certain degree, silicon is already designed with thermal migration in mind. It’s what we call ‘dark’ silicon, essentially silicon that is disabled/not anything that acts as a thermal (or power/electrical) barrier between different parts of the CPU. Modern processors already have copious amounts of dark silicon, and as we move to denser process node technologies, it will require even more. The knock on effect on this is die size, which could also affect yields for a given defect density.

Despite these thermals, none of our benchmarks (either gaming or high-performance compute) seemed to be out of line based on expectations – if anything the 10850K outperforms what we expected. The only gripe is going to be cooling, as we used an open test bed and arguably the best air cooler on the market, and users building into a case will need something similarly substantial, probably of the liquid cooling variety.

Intel Core i9-10850K Review CPU Tests: Microbenchmarks
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  • edzieba - Monday, January 4, 2021 - link

    I dunno, sounds like an opportunity for ambient-pressure water phase-change cooling to me! Who needs evacuated heat-pipes or vapour-chambers when you can just spray the top of the IHS directly!
  • shabby - Monday, January 4, 2021 - link

    Hey Ian can you put the real cpu wattage in the charts that the cpu used in that test rather than the fake one? We all know this cpu never uses 125 watts.
  • Drkrieger01 - Monday, January 4, 2021 - link

    You either skipped the 'Power Consumption' page, or don't understand CPU TDP ratings. The '125W' rating is the 'non-turbo' rating, meaning power consumed at max non-turbo clock rate. AMD does the same thing, and also has a higher power consumption during turbo (although not anywhere near as much as Intel does).
  • shabby - Monday, January 4, 2021 - link

    Since each benchmark varies it would be nice seeing how much wattage each cpu used during that benchmark.
    Yes i know amd uses more power during turbo, the 5950x uses 30 watts more than advertised... compared to ~140 watts more that intel advertises their 10850k to use. That quite the difference don't you think?
  • Drkrieger01 - Monday, January 4, 2021 - link

    Unless you're working on a power budget, I honestly wouldn't worry about it. Most review websites don't have the time/man-power to trace the power usage on each benchmark for each CPU. You will also have a variance between processors of the exact same model due to binning/silicon lottery. You're better off planning to use/dissipate the full turbo power of the CPU than hope for lower power. Or just buy an AMD (if you can find one!)
  • eek2121 - Monday, January 4, 2021 - link

    Actually AMD chips use the TDP value as the maximum power value minus the IO power, so all AMD chips use a total of 143 watts at maximim.
  • Flunk - Monday, January 4, 2021 - link

    Intel seems to have six similar i9 SKUs with prices ranging from $453 to $488. Seems rather pointless. Maybe Intel marketing should spend some time thinking about whether or not their insanely complex model scheme is contributing to their lack of sales. AMD has ONE SKU that competes with all of those Intel SKUs. Clock down for lower TDP doesn't need to be an entire SKU.
  • Duwelon - Monday, January 4, 2021 - link

    Whoever comes up with Intel's SKUs must be the same person/people responsible for interfacing with USB Implementers Forum on Intel's behalf. The industry is replete with remarkably confusing naming schemes, seemingly on purpose.
  • DanNeely - Monday, January 4, 2021 - link

    Making the low power versions use the same model number would be a very anti-consumer move because you'd have no easy way to know if you were getting the 3.7Ghz or 1.9Ghz model. We already have that problem on mobile where two laptops with identical specs perform wildly different because one is running the CPU at 2x the power/performance of the other. Using separate model numbers also lets you bin chips that perform best at low and high power levels separately.

    The production limit bins (10850K and both IGPless KF models) muddle things up a bit; but Intel's desktop lines are very cleanly broken out vs what they did a decade+ ago with a mess of different similar chips with varying cache sizes and clock speeds but the same core counts; or the ongoing mess of their mobile line (good luck figuring anything out about one of those chips from its model number without looking it up).
  • Crazyeyeskillah - Monday, January 4, 2021 - link

    they have various skus for oem's, system builders, general public, retail products, ect ect

    Certain OEMs require a non-open market skus to promote their products or run at certain specs that differentiate them from what's available on the open market.

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