[dcow]

> In other words, the laptop will throttle back performance automatically regardless of the settings you chose.

So if you change the performance settings they allow the laptop to draw 10W from the battery while plugged in for a little bit but it will throttle down to 95W to keep itself running. It still throttles which is I think the GGP’s point.

[dragontamer]

The point is that a laptop with a 65W power adapter can in fact, draw 90W (or more) for a period of time in practice.

Which means, we don't really have a good way to benchmark power usage on laptops in a practical sense. We'd likely need to bust out the soldering iron + oscilloscope and measure currents entering the laptop's VRMs to accurately measure power usage over time.

I know laptops / cores have an "amp-counter" on board somewhere, but there's no guarantee that these devices are consistent or accurate across different laptops. Its sufficient for measuring how much energy different bits of code has (ex: Linux powertop tools), but not sufficient at comparing Apple M1 vs AMD Zen3 chips. We need a 3rd, trusted and independent measurement of power usage.

We can't just assume a 65W power adapter leads to 65W peak usage. Perhaps in the past when laptop designs were more in spec that was a decent assumption. But that time has passed, and today's laptops often do peak at power usages far in excess of their charger capacities (albeit temporarily, but even then, that makes measurements / benchmarks very difficult).

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I guess if you physically remove the battery pack (is that still allowed on these laptops?) and then plug it in, we might be getting somewhere. But the Macbook Pro doesn't have an easily removable battery pack.

[cwizou]

Completely agree on everything.

That's the reason we didn't review laptop CPUs when I reviewed CPUs. You can get exact CPU power draw on a desktop motherboard (by using an amp clamp on the P8 connector) but it's hard (or not possible) to do that across multiple laptop chassis.

Removing battery (when possible) is not a solution either as what you get may differ a lot from classic "plugged in" usage (see the references to the MacBook Pro and Dell that used an i9 that still drained the battery when plugged in, because they can use more power than the power adapter brings).

On top of that, way too much depends on the OEM design and the performance of a given CPU will greatly vary from one chassis to another, because of the various throttling mechanism and the various configurable things that OEM can do (it's not just the cTDP, you can as an OEM play with various turbo times, another person mentionned P2 states, which is one of those).

So a given mobile CPU performance means nothing at the end of the day, only the laptop "as a whole" can be measured, which is why you don't see good quality benchmarks of mobile CPUs.

Anyway, just a small complement :

> laptops / cores have an "amp-counter" on board somewhere

Intel (and AMD to some measure) CPUs all have various sensors on chip that gives you the power consumption in watts (or amps, depending). They can be read with software such as hwinfo [1].

Those are usually not incredibly reliable though, they are not calibrated per CPU and it's very much a guestimate that could easily be in some cases +/- 5W off.

So sadly, not usable either (especially on mobile).

[1] : https://www.hwinfo.com/