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Exploring CPU Energy Scaling On Core i9-13900K and Ryzen 9 7950X

One of many greatest operating gags on social media and Reddit is how sizzling and energy hungry CPUs have develop into through the years. Whereas at one time flagship x86 CPUs did not even require a heatsink, they’ll now saturate complete radiators. Fortunately, it is not fairly to the degrees of a nuclear reactor, because the memes go – however as the children say as of late, it is also not a nothingburger. Designing for greater TDPs and higher energy consumption has allowed chipmakers to maintain pushing the envelope by way of efficiency – one thing that is no straightforward feat in a post-Dennard world – but it surely’s definitely created some new complications relating to energy consumption and warmth within the course of. One thing that, for higher or worse, the most recent flagship chips from each AMD and Intel exemplify.

However regardless of these normal traits, this doesn’t suggest {that a} excessive efficiency desktop CPU additionally must be an influence hog. In our evaluation of AMD’s Ryzen 9 7950X, our testing confirmed that even capped at a as of late pedestrian 65 Watts, the 7950X may ship a major quantity of efficiency at lower than half its regular energy consumption.

For those who’ll pardon the pun, energy effectivity has develop into a sizzling speaking level as of late, as fans look to save lots of on their vitality payments (particularly in Europe) whereas nonetheless having fun with quick CPU efficiency, searching for different methods to make the most of the total silicon capabilities of AMD’s Raphael and Intel’s Raptor Lake-S platforms moreover stuffing the chips with as many joules as doable. All of the whereas, the small kind issue market stays a steadfast outpost for prime effectivity chips, the place cooler chips are essential for constructing smaller and extra compact techniques that may forego the necessity for big cooling techniques.

All of that is to say that whereas it is nice to see the envelope pushed by way of peak efficiency, the standard deal with how an unlocked chip scales when overclocking (pushing CPU frequency and CPU VCore voltages) is only one method to take a look at general CPU efficiency. So right this moment we’re going to go the opposite method, and to check out general vitality effectivity for customers – to see what occurs once we intention for the candy spot on the voltage/frequency curve. To that finish, right this moment we’re investigating how the Intel Core i9-13900K and AMD Ryzen 9 7950X carry out at completely different energy ranges, and to see what sort of advantages energy scaling can present in comparison with inventory settings.

The Ever Altering Definition of TDP (Thermal Design Energy)

One of the vital irritating speaking factors surrounding processors includes TDP, or extra particularly, what TDP even is. Whereas the time period has a set definition – Thermal Design Energy – what that really means regarding the specs of a product varies from one {hardware} maker to the subsequent. Even Intel and AMD have barely completely different definitions of TDP (regardless of sharing the x86 CPU market), which makes it an advanced and at-times complicated time period. Briefly, TDP is not an unflinching information to the utmost energy consumption from a selected processor – and even how a lot warmth vitality can dissipate from a processor

That is is a matter we’ve given loads of column inches to through the years, so beneath are some earlier articles with regards to energy and TDP:

Beginning with Intel, whereas the corporate assigns official TDP figures to its processors, the fact is that their unlocked processors should not restricted to at least one assigned energy determine. At finest, Intel affords a set of TDP values based mostly across the base frequency of their chips, whereas energy degree 1 (PL1) and energy degree 2 (PL2) scores are laid on prime of that to outline the facility parameters for these all-important (and all-advertised) turbo clock speeds.

In the meantime, taking a look at how AMD defines its TDP figures has been made harder with the release of its Ryzen 7000 series processors and the accompanying AM5 platform. Whereas AMD does give out default TDP figures the Ryzen 7000 sequence, that is no extra a tough ceiling than it’s with Intel; the opposite component is what AMD calls Bundle Energy Monitoring, or PPT for brief. The outlined TDP worth is assigned to its processors based mostly on default frequency ranges, whereas PPT is outlined because the limitation to what the precise socket can ship by way of energy (and what flagship chips tuned for max efficiency will attempt to devour).


The lengthy and wanting issues is that, on virtually any consumer-level motherboard paired with an sufficient cooler, utilizing any unlocked processor, together with the 2 we’re specializing in right this moment, will circumvent the chip’s base TDP score in an effort to present the best turbo clock speeds doable, capped solely by the temperature and electrical supply limits. So taking the Ryzen 9 7950X for instance, though the default TDP is 170 W, the precise PPT wattage is outlined as 230 W (with a sustained present of 160 A).

The excellent news, nevertheless, is that these energy limits are simply user-adjustable on each AMD and Intel platforms. Many motherboards for each platforms provide a plethora of adjustable values to boost and decrease these limits, and even inside Home windows there are software program packages like AMD’s Ryzen Grasp and Intel’s XTU that may make the required adjustments.

Discovering The Candy Spot Stability Between Efficiency, Energy, and Warmth

For its newest sequence of processors, AMD is providing a brand new function known as ECO Mode, which reduces a 170 W TDP-rated processor to 105 W (and a 105 W TDP-rated processor right down to 65 W). Once we reviewed the AMD Ryzen 9 7950X processor, we discovered some fascinating outcomes when utilizing it at 65 W as a substitute of its default worth of 170 W.

An important factor we noticed was that at 65 W, the Ryzen 9 7950X processor outperformed the Intel Core i9-12900K at default settings within the CineBench R23 multi-threaded check, which is nothing wanting spectacular. Since then, Intel released its 13th Gen Core series codenamed Raptor Lake, so the general enjoying subject has been leveled some. However nonetheless, it exhibits the potential worth in dialing down the facility consumption of a flagship CPU, because the 7950X was capable of ship 80% of its peak efficiency at underneath half the facility consumption.


These findings, in flip, impressed the thesis behind this doing this text: we questioned how each the Core i9-13900K and Ryzen 9 7950X carried out when utilizing it with varied energy restrictions utilized. So for this text, we’re going forward and testing simply that state of affairs, operating AMD and Intel’s flagship CPUs are varied energy ranges.

We have chosen a number of energy limits/PPTs to check, together with the next:

  • Intel Core i9-13900K at default settings (125 W base, 253 W turbo)
  • AMD Ryzen 9 7950X at default settings (170 W base, 230 W PPT)
  • Each at 125 W
  • Each at 105 W
  • Each at 65 W
  • Each at 35 W

All through all of this, it is vital to notice that the Intel Core i9-13900K and AMD Ryzen 9 7950X have a essential distinction by way of building: chiplets. Whereas the Core i9-13900K is a monolithic design with cache, core, reminiscence controller (IMC), and iGPU all being constructed inside a single die, AMD’s Ryzen 9 7950X is constructed upon a chiplet design. In consequence, the 7950X makes use of three completely different chiplets for all of its main capabilities, with two eight-core core advanced dies (CCD) and one IO die (IOD) containing the reminiscence controller, PCIe, and graphics.

A screenshot from AMD’s Ryzen Grasp Overclocking software program throughout testing

Which means that when setting an outlined energy restricted with the Core i9-13900K, it is limiting energy from all the variables as talked about. Whereas doing the identical on the Ryzen 9 7950X would not yield the fairly identical impact, because the IOD and CCDs function semi-independently, albeit by way of AMD’s Infinity Cloth interconnect. To correctly restrict the facility on the Ryzen 9 7950X, the Bundle Energy Monitoring restrict would have to be utilized to constrict the facility limits correctly, comparable to setting a price of 125 W on the PPT and never simply on the CPU cores.

Take a look at Mattress and Setup

Since each Intel and AMD use completely different platforms and sockets, we’re utilizing the MSI MPG Z790 Carbon WIFI for the Core i9-13900K and the GIGABYTE X670E Aorus Grasp for the Ryzen 9 7950X. To attempt to maintain issues on a degree enjoying subject, we’re utilizing an SK Hynix Platinum P41 2TB NVMe storage drive and AMD Radeon RX 6950 XT graphics card.

Usually we might depend on JEDEC reminiscence settings outlined by every platform, however on this case, we have opted to check each platforms with the identical SK Hynix DDR5-5600B CL46 reminiscence configuration. That is the reminiscence we used for the Intel Core i9-13900K evaluation, but it surely’s quicker than the best official JEDEC settings supported by AMD’s Ryzen 7000 sequence platform (DDR5-5200). Both method, we needed to make our comparisons as apples-to-apples as doable, together with holding reminiscence at a relentless efficiency and energy degree to research the advantages (if any) of limiting system energy draw.

Energy Scaling Take a look at Mattress (DDR5)
Intel & AMD
CPUs Core i9-13900K ($589)
24 Cores, 32 Threads
125 W Base, 253 W Turbo

Ryzen 9 7950X ($699)
16 Cores, 32 Threads
170 W Base, 230 W PPT

Motherboards MSI MPG Z790 Carbon WIFI (13900K)
GIGABYTE X670E Aorus Grasp (7950X)
Reminiscence SK Hynix
2×16 GB
DDR5-5600B CL46
Cooling EKWB EK-AIO Elite 360 D-RGB 360mm 
Storage SK Hynix Platinum P41 2TB PCIe 4.0 x4
Energy Provide Corsair HX1000
GPUs AMD Radeon RX 6950 XT, 31.0.12019
Working Techniques Home windows 11 22H2

Relating to benchmarks, we have opted for a small collection of rendering and encoding exams as we imagine these will spotlight variations in processor efficiency on the completely different energy ranges. For gaming, we have opted for Whole Conflict: Warhammer 3, as it is a notoriously closely CPU-dependent title, whereas Borderlands 3 is extra graphically demanding. We thought it might be prudent to check certainly one of every, though if anybody want to request extra titles from our CPU 2023 benchmarking suite, be at liberty, and we’ll add knowledge as we discover the time to gather and collate it.

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