TDP means what it always has. It's the maximal thermal power output of the processor. Input electrical power may fluctuate, but TDP was never an electrical parameter.

On modern Intel processors, TDP isn't the maximum thermal output power of the processor. It's the thermal output power when it's throttling back its speed by a particular, arbitrarily-defined amount for thermal reasons. It's basically a marketing number. The electrical input power on the other hand is pretty close to the actual thermal output power and is roughly the number you should actually use when speccing out a cooling system for an Intel processor.

The difference between input power and thermal output of a CPU is negligible. A tiny amount of electricity is used for external signalling, the rest gets converted to heat. So in practice TDP can be treated as a limit on input power. In fact that's exactly what Intel CPUs do by setting PL1 equal to TDP by default.

Negligible over time. What has everyone inexplicably confused is that electrical draw is allowed to be higher instantaneously than the output cooling will allow to accommodate bursts of computation. And some how everyone thinks that's a bad thing.

Again, TDP means the same thing now that it did 15 years ago.

What you've described is how it used to be, maybe you gets few seconds of usage over the TDP, but then the processor throttles back to hit the spec. That can still happen (and often does in laptops etc), but as described in the article, and many others, many to most motherboards sold as individual components are configuring the chips so that they will run at a higher power state for an indefinite time, so long as the temperatures stay within operating limits.

It would be nice to know what the expected power input / heat output is in that state, so you can get cooling to match, and have it in turbo mode at all times when the CPU is being stressed.

Cooling to the TDP only will (or should) get you the base clocks and a brief amount of turbo, but is likely to thermal throttle quickly.

This also brings more into question the adequeacy or not of the thermal interface material used between the CPU die and the heatspreader -- if the CPU will run turbo for longer if you keep it cooler, there's more frustration about less heat efficient solutions.

Shouldn't chip makers provide you a Max power usage number so you would know what power supply you need, if the CPU can draw double for an interval, then the GPU would do the same and your power supply does not enough extra power you maybe in trouble.

The "scandal" was caused by the fact reviewers were getting different results and people would accuse people on not doing the benchmark right.

Exactly. All of this confusion is from some expectation that "TDP = input power", which is totally incorrect.

It's how much it's designed to dissipate right? Which depends on the cooling so by your meaning it's a vague number isn't it?

I think from power/watt number on a cpu people expect two thing. How efficient it is for the performance (electric bill) where you need input power. How better a cooling I need will need the thermal power.

But even with that the issue of Turbo makes it harder to quantify those two because it all depends on workload. If I recall correctly though even with all that if I understand correctly the peak power draw in intel gets throttled much easier than AMD whereas their TDP number (compared to AMD) artificially inflates their efficiency reputation. I do think they had been much more efficient than AMD specially pre Zen.

In that case, reviewers and tech sites should either prioritize peak power or at least mention peak power numbers every single time TDP is mentioned, too, because peak power is at least as important as TDP. I know from past experience with laptops that tend to get hot, that if the laptop uses significantly more power than what you'd expect from the TDP, you will have a bad experience as a customer with that laptop. So at this point, TDP is definitely quite misleading to customers. Either scrap it completely or at least mention a more relevant metric to consumers.

> that if the laptop uses significantly more power than what you'd expect from the TDP

You're falling into the "TDP is power input" trap.. TDP and power input are not the same. You can have a chip that takes less power to operate at a TDP equivalent to another chip which takes more power to operate.

Edit: There is no way that 100% of output power in a CPU is thermal, else it would be nothing but a very expensive heater. Also, CPUs do not operate in a closed environment, like those replying to me here seem to think.

Input power equals output power is a fundamental physical rule, not a "trap". Yes, average (thermal) output power does not equal instantaneous (electrical) input power (ie thermal mass), but it averages out.

What the article is pointing out that TDP is thermal design power. Meaning a nameplate value that was targeted for "standard" operation, even though the processor can do higher. So if something has a TDP of 100W, yet the heatsink can maintain proper operating temperature while dissipating 150W, then the processor might sit there drawing (and dissipating) 150W the whole time.

As an aside, I really wish CPU cooler manufacturer/reviews would start simply stating the thermal resistance - basically the single number that characterizes its effectiveness. I know it would undermine the dog and pony show of building a test system with so-and-so's motherboard etc running benchmarks, but the entire goal of science is to weed out the extraneous narrative.

> Input power equals output power is a fundamental physical rule, not a "trap"

No shit. The trap is thinking that all output power is thermal (it's not).

CPUs do no thermodynamic work. They do computational work, which does not count as work in work-heat-energy balance. All electrical energy consumed by CPU turns into increased internal energy of the surroundings, which is, in short, called heat.

Not all of the electrical energy consumed by the CPU is used by the CPU for computational work. Some of the electrical energy transfers out of the CPU to other components. The TDP of the CPU is not concerned with those other components. TDP is not a useful measurement of the amount of electrical energy a CPU can consume.

All consumed energy is used to produce heat, by definition of "consumption". If some electrical energy transfers out of CPU to other components (this is indeed possible), then by definition this energy is not consumed by the CPU. The meaning of TDP is explained in the article - Intel's value of TDP was such a measure, but is no longer so.

All output power is thermal though. This is basic thermodynamics. A negligible amount of input power will be distributed outside of the CPU die which will be dissipated as heat a short distance away. Pray tell, what other energy form do you think this input is becoming anyway?

I imagine some tiny percentage would instead be dissipated as light/radio waves or sound too - hence my ~99% comment.

There's also this: (https://en.wikipedia.org/wiki/Landauer%27s_principle) if you want some light reading.

Indeed there will be some piezoelectric effect and some EM emissions on the order of micro watts compared to the 10s of watts burned by the CPU. But the poster I was replying to seemed quite confused about the fate of power in a CPU used for computation: It’s dissipated as heat.

Well some power is used to run the fans which ends up partly turning into kinetic energy of air leaving the case. Sure, that may also manifest itself as heat somewhere down the line, but not in a way that is relevant for this discussion (and indeed you have to draw the line somewhere).

It's probably fairly neglible though, probables less than a watt in most systems.

The fans aren't the CPU.

Oops, you are right.

In a CPU ~99% of it should be, how else is the power dissipated?

Where else would it be going to? The RGB LEDs?