One of the hardest things to determine about a processor is its load power consumption. That’s doubly true for Intel’s 10th Gen CPUs. While the marketed TDP is usually around 95-125W, under load, most high-end chips consume as much as 225W. The 10th Gen processors take it to another level, with the Core i9-10900K drawing as much as 260W under load while the Core i7-10700K can go as high as 229W. So why do Intel’s high-end processors draw so much power and what exactly is the power management profile of these chips like?
For starters, you should know that this isn’t an anomaly or malfunction. The spec TDP of Intel CPUs pertains to the power draw at stock frequencies. When the CPUs boost to higher “Turbo Frequencies”, the power draw increases considerably. This power state or profile is called PL2 (Power Level 2) while the stock (marketed) power state is called PL1.
Then there’s Tau which determines how long will your chip stay at the boosted “PL2” state. When you first boot your PC, the CPU power limits will be set to PL2, much higher than the spec PL1 limits. Depending upon the load, your processor will engage one or more cores and boost to the rated Turbo Frequency. In most single to quad-threaded applications, the CPU power draw will stay under PL2 despite reaching the maximum Turbo Boost frequency.
However, when you’re running a more intensive multi-threaded application, say Cinebench or 7-zip, all your CPU cores will kick into action. In such a scenario, the power draw will quickly soar up to the PL2 limit and the processor will reduce the all-core frequency to keep the power draw in check.
Under standard conditions, the processor would adhere to the PL2 power state and the accompanying boost frequency for a duration “Tau”, usually 56 seconds, and then return to PL1 (stock), thereby reducing the clock speed to the base frequency. This would continue till the intensive workload is completed and the CPU returns to idle. After that, it’d return to PL2 power limits and repeat the above-explained behavior.
However, for better or for worse, Intel doesn’t enforce the PL2 and Tau values, and motherboard vendors are free to set them as they choose in the firmware. As such, most high-end Z series motherboards have a PL2 and Tau values much higher than the ones prescribed by Intel. For example, the Core i9-9900K has a PL2 value of 119W, but most OEMs set it as high as 160 or 180W while making Tau infinite.
Therefore, if you’re running a high-end K series processor on a Z490 motherboard, chances are that it won’t adhere to the Intel recommended values of PL2 and Tau. In most cases, your CPU will run at the maximum Turbo Boost clock (PL2 power state) for infinity or as long as the thermals allow it (while ignoring the Tau time limit).
While this may seem like an easy way to boost performance, it makes it hard to standardize the TDP and compare the efficiency/power draw across different systems.
|10th Gen Processor||PL1 Power (W)||PL2 Power (W)||Tau (Seconds)|
|Core i5-10600, Core i5-10500, Core i5-10400||65||134||28|
|Core i3-10320, Core i3-10300, Core i3-10100||65||90||28|
|Pentium Gold 6500, Pentium Gold 6400, Celeron G5920, Celeron G5900||58||58||28|
|Pentium Gold G6500T, Pentium Gold G6400T, Celeron 5900T||35||42||28|
The reason why motherboard vendors do it is rather straightforward: To get ahead of the competition. They include multiple-phase VRMs on their flagship offerings with 10+ power phases, thereby safely increasing the PL2 power draw and allowing the processors to boost to the max frequency, indefinitely.
As long as you’re not hitting the thermal limits, this means most high-end Intel processors will draw a lot more power than spec and boost to Turbo frequencies much more often and for longer. It’s only in notebooks and handheld devices where the thermals and battery life are a concern that the Intel recommended PL2 and Tau values are enforced by OEMs. In the desktop space, it’s all fair game.
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Title: Intel 10th Gen CPU Power Consumption Explained: PL1, PL2, and Tau
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Published Date: Sun, 10 Jan 2021 12:17:37 +0000