[ewg4345h43]

I don't think that this is correct. My laptop, Lenovo P14S GEN 2 AMD with 5850U CPU has 65 WATT USB-C power adapter. Half of that power will be consumed by monitor (4K and 500 cd/m²) and you write above that the whole system should consume 65 WATT... This is not possible at all, because there is only 30-35 WATT left for the whole system except monitor.

[mgraupner]

If your system exceeds the maximum amount of power provided by the power adapter, it will use the internal battery. Otherwise it will throttle the CPU.

[dcow]

Laptops are not designed to do that under consumer operating conditions (they can, sure, but they won’t). No manufacturer will ship you a system with an adapter that can’t power the machine at peak load.

[mgraupner]

That is not true, Apple laptops (and probably others) are known exactly to do this. The infamous i9 MacBook Pro 16" could definitely use more power than the supplied power adapter and drain the batterie under load. And that was perfectly within its specification.

[errantblaze]

The Dell G5 15 is designed to do that and the feature is called hybrid power mode.

https://www.dell.com/support/kbdoc/en-us/000140513/gaming-la...

[dcow]

This one honestly reads more like a “we fucked up let’s call it a feature in an obscure technical amendment”.

[cwizou]

You'd be surprised, this is how most modern "high end" Intel laptop actually works. Even some Intel Macbook Pro exhibited this.

This is 100% an Intel thing.

[errantblaze]

Another possibility is cost reduction as these are lower-end models. At least some of higher-end models (G7 and Alienware) have 180W and 240W power adapters, instead of the 130W included with this model.

[dragontamer]

Counterpoint:

https://www.pcmag.com/news/gaming-on-surface-book-2-drains-b...

[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).

--------

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/

[jclardy]

But the M1 air charges and runs simultaneously on a 30W USB-C power brick…it has a slightly dimmer display at 400 nits.

[snazz]

I've even plugged my M1 Air into the 20W USB-C iPad charger with no ill effects (somewhat slower charging while it's in use). It's possible that the battery would stop charging or deplete if I had the brightness cranked all the way up and the CPU was doing something intensive.

[cwizou]

Check the sibling comments, your CPU (like most mobile Intel/AMd) can be configured for different TDPs by the OEMs, so you can't compare anything, especially not PassMark results.

[ewg4345h43]

Yes, you can throttle the CPU, but then the CPU scores in Benchmarks will be lower and that's not the case... (Benchmarks are collected from different machines). So it looks the Macs consume pretty much the same amount of power.

[cwizou]

No, the TDP is configurable up to 25W (and down to 10). Again check the link of the score distribution I put in another comment, it's all over the place, and the passmark results are not a reliable comparison at that point.

[ProfessionalHat]

No. AMD Ryzen™ 7 PRO 5850U can boost upto 4.4Ghz, likely it would be consuming upwards of 50W for that short duration.

An easy way to verify it, is to measure the benchmark delta when on battery and when connected to an external power source. (M1 benchmarks remains almost the same)

Intel i7 9750H for example has a P2 of above 80W and only then can it break the 4Ghz barrier. Even though the processor is technically rated only 45W. At 45W it can just maintain the base clock i.e. 2.6Ghz on all cores.

M1 is much more efficient than any x86 chip on the market right now.

[smoldesu]

The M1 is hitting 4gHz across only 4 of it's cores, whereas the 9750 is driving 6 (and 12 threads on top of that). Furthermore, the M1 will have no problem hitting ~20w during peak load, so frankly the math checks out to me. The comparison definitely starts to deteriorate once you consider that the M1 is ~3x as transistor-dense as the Intel chip, and part of me actually wonders why they didn't get more power out of a chip that only needs to worry about a handful of instructions and doesn't know about hyper-threading.

[saagarjha]

Pretty sure M1 does not hit that frequency on any of its cores…

[smoldesu]

I was under the impression that the performance cores had hit 4.1gHz before, is that incorrect?