Intel's 12th Gen Intel Core "Alder Lake" processors mark the company doing away with thermal design power (TDP) as a specification reported to consumers. This is among many firsts introduced by these chips, such as heterogeneous multi-core, new-generation I/O, etc. Over the past several weeks, we've been studying various aspects of Alder Lake, and one lingering since our main launch-day review is the mysterious new power-management configuration of these processors.
For the better part of microprocessor history, TDP has been a measure of a chip's heat output, which is correlated with power draw. With the growing complexity of processors, such as the addition of multiple cores, integrated core-logic, integrated graphics, etc., resulting in today's processors essentially being system on chip (SoC), TDP has been systematically losing relevance. A processor marked "65 W" on the box doesn't necessarily stay below that power draw at all times. Rather, it can go far beyond that in short bursts. The idea here is that the heatsink has some mass that can absorb a certain amount of heat before temperatures rise significantly. So even if 200 W of heat are dumped into the cooler for only a few seconds, overall temperatures will barely be affected, and the cooler will remain adequate.
Above is a chart from our Intel Core i9-10900K review that explains how this "extra heat output" system works. When a demanding workload starts, the CPU will run at its PL2 power limit, which is a value that's much higher than the standard-rated TDP, 250 W vs. 125 W in the chart above. After a few seconds, a specific duration called "Tau," the boosting headroom, is used up, and the processor will drop back down to its default power limit (PL1). It will sustain that heat output indefinitely until the workload ends.
With Intel 12th Gen Alder Lake processors, two new terms are introduced that replace TDP: "Processor Base Power" and "Maximum Turbo Power." In Intel's own words:
Processor Base Power
The time-averaged power dissipation that the processor is validated to not exceed during manufacturing while executing an Intel-specified high complexity workload at Base Frequency and at the junction temperature as specified in the Datasheet for the SKU segment and configuration.
Maximum Turbo Power
The maximum sustained (>1s) power dissipation of the processor as limited by current and/or temperature controls. Instantaneous power may exceed Maximum Turbo Power for short durations (<=10 ms). Note: Maximum Turbo Power is configurable by system vendor and can be system specific.
So let's translate this. "Processor Base Power" is a vague "typical" power draw value at an undisclosed Intel workload that's definitely "optimized" to return the desired 125 W value. It's interesting that the i9-12900K, i7-12700K and i5-12600K all run at the same 125 W value in this special workload despite their completely different performance characteristics. "Maximum Turbo Power" is the real limit, the maximum amount of power the processor can draw at stock settings for an indefinite duration of time.
For the i9-12900K, this is 241 W. Unlike past generations of processors that were constrained by the Tau time value to hold maximum power draw, or PL2, Alder Lake processors now run at maximum power draw indefinitely if the load demands it and as long as the processor doesn't hit the thermal limit of 105°C. This is done without inventing a new system; Intel simply tweaked the PL1 and PL2 values and set them both to 241 W, which effectively means the processor can run at 241 W all the time as long as it doesn't overheat. The "125 W" limit now only exists on paper and in marketing documents.
Just like on previous Intel CPUs, the PL1 and PL2 values are fully adjustable even on non-K SKUs. In this article, we test a Core i9-12900K processor with various power limits ranging between 50 W to 241 W, which include 75 W, 100 W, and 125 W. We're also including 190 W, which is the rumored power limit setting of the upcoming non-K Alder Lake processors. All these results are compared with an untouched stock Core i9-12900K and various other processors across a big selection of our processor test bench. On its part, Intel strongly recommends you leave the power management settings untouched for the best performance, but there are many practical applications of limiting power, such as working off a power inverter on an expedition vehicle or leaving your machine on at night, where you absolutely don't want a dormant background app or Windows housekeeping task to leech power.
SuperPi is one of the most popular benchmarks with overclockers and tweakers. It has been used in world-record competitions since forever. It is a purely single-threaded CPU test that calculates Pi to a large number of digits—32 million for our testing. Released in 1995, it only supports x86 floating-point instructions and thus makes for a good test for single-threaded legacy application performance.