"Compare the 7945HX3D to any Apple CPU on the same 5nm process with a similar TDP and the 7945HX3D will generally have similar if not better performance."
Sounds interesting, do you have numbers - s I get this argument often, that on the same node, Apple is so much better.
So here's each vendor's first CPU on TSMC 5nm. This is actually the only process they've both used, and AMD only used it for a couple of models -- they tend to use all the ones Apple doesn't (7nm, 6nm, 4nm vs. 5nm and 3nm), which makes direct comparisons rare. But this is one:
You have to be careful of citing spec-sheet TDPs because AMD allows their CPUs to boost way above the configured TDP where for apple it’s normally obeyed, and usually not reached unless it’s a mixed cpu-gpu load like gaming.
Pointing to TDP as if it meant anything compared to actual power measurements is usually a mistake. It doesn’t mean anything anymore. I really hate it as much as anyone else, I love architectural comparisons/etc... but you have to look at actual measurements from actual devices in a particular workload. Which, again, is very unfortunate since most reviewers don't do that, certainly not for more than one or two workloads.
Cinebench R23 is also not a particularly great test compared to SPEC2017, Geekbench 6, or Cinebench 2024, and most vendors still haven’t switched over even to the newer CB2024. Generally the older tests tend to give x86 a bit of a boost because of the very simple test scenes/lack of workload diversity.
(I was looking at this when M3 Max MBPs came out and 7840HS was the current x86 hotness etc... just very few reviewers with direct CB2024 numbers yet and fewer with actual power measurements, let alone anyone having any other workload benched... geekerwan and notebookcheck seem to be the leaders in doing the actual science these days... save us, Chips And Cheese...)
> You have to be careful of citing spec-sheet TDPs because AMD allows their CPUs to boost way above the configured TDP where for apple it’s normally obeyed
This is more Intel than AMD. AMD will generally stick to the rated TDP unless you manually reconfigure something.
> and usually not reached unless it’s a mixed cpu-gpu load like gaming.
For mobile chips you'll generally hit the rated TDP on anything compute-bound in any way, simply because the rated TDP is low enough for a single core at max boost to hit it. And you'll pretty much always hit the rated TDP on a multi-threaded workload regardless of if the GPU is involved because power/heat is the limit on how high the cores can clock in that context, outside of maybe some outliers like very low core count CPUs with relaxed (i.e. high) TDPs.
> you have to look at actual measurements from actual devices in a particular workload.
But then as you point out, nobody really does that. Combined with the relative scarcity of parts made on the same process, direct comparisons of that kind may not even exist. Implying that the people saying the Apple processors are more efficient on the same process are doing so with no real evidence.
> This is more Intel than AMD. AMD will generally stick to the rated TDP unless you manually reconfigure something.
no, it's generally the opposite. Intel tends to exceed TDP substantially due to boost, and AMD actually exceeds it by greater margins than Intel.
This is consistent across both desktop and laptop, but AMD's mobile SKUs are actually allowed to exceed TDP by even larger margins than the desktop stuff.
I've done the measurement myself with an AC watt meter and CPUs generally hew pretty close to their TDP. 65W CPU under load with a full-system power consumption around 70-75W, with the balance presumably being things like the chipset/SSD and power supply inefficiency.
But the TDP is also configurable. It's one of the main differences between different model numbers with the same number of cores which are actually based on the same silicon. The difference between the 4800U and the 4900H is only the TDP and the resulting increase in clock speed. But the TDP on the 4900H goes up to 54W.
Whereas the TDP on the 4800U they tested there is configurable even within the same model, from 10-25W. And then we see it there using a sustained 20-25W, which is perfectly within spec depending on how the OEM configured it. And there is presumably a setting for "use up to max power as long as not thermally limited", which is apparently what they used, and then combined it with a 15W cooling solution. Which is what you see clearly in the first graph on the same page:
It uses more power until the thermal solution doesn't allow it to anymore.
In the second test it can sustain a higher power consumption, maybe because the test is using a different part of the chip which spreads the heat more evenly instead of creating a hot spot. But this is all down to how the OEM configured it, regardless of what they advertised. That CPU is rated for up to 25W and is only using 22. Obviously if the OEM configures it to use more, it will.
yes, but if the 7945HX3D is running at 112W (75W cTDP + AMD allows unlimited-duration boost at 50% above this) and the macbook is running at 50W cpu-only (70W TDP) then the macbook is actually substantially more efficient in this comparison.
That's why I said: you have to look at the actual power measurement and not just the box spec, because Apple generally undershoots the box-spec for cpu-only tasks, and AMD always exceeds it substantially due to boost. Obviously if you give the AMD processor twice the power it's going to be competitive, that's not even in question here. The claim was, more efficient than Apple - and you simply cannot assess that with the box TDPs, or even cTDPs, because x86 processors make a mockery of the entire concept of TDP nowadays.
(and it didn't use to be like that - 5820K and 6700K would boost to full turbo under an AVX2 all-core load within the rated TDP! The "boost power is not the same thing as TDP" didn't come around until Ryzen/Coffee Lake era - accompanied by ploppy like "electrical watts are not thermal watts" etc)
edit: notebookcheck has cinebench R15 at 36.7 pt/w for M3 Max and 33.2 pt/w for 7840HS, and 28 pt/w for Pro 7840HS (probably a higher-cTDP configuration). Obviously CB R15 is miserably old as a media benchmark, but perhaps ironically it might be old enough that it's actually flipped around to being more representative for non-avx workloads lol.
CB24 MT at 50% higher for M3 Max and CB R23 at 11% higher (shows the problem there with x86 processors on R23). Looking back at Anthony's review-aggregator thing... they're using the highest score for 7840HS I would assume (it's 1k points higher than median on notebookcheck) and also they're probably comparing box TDPs, which is where the inversion comes from here (from parity to a 10%-ish lead on efficiency). Because actual measurements of the M3 Max, from actual reviewers, have CB 2024 at around 51W all-core, and it almost doubles a 7840HS's score there.
And looking at it a little further even that nanoreview aggregator thing doesn't claim 7840HS is more efficient... they rate the M3 Max as being 16% more efficient. Seems that is a claim Anthony is imputing based on, as I said, box TDP...
edit: I’m also not even sure that nanoreview article has the right TDPs for either of them in the first place…
OT: I think it also shows the bad iGPU compared to Apples offerings, so too many x86 laptops have additional GPUs, which reduces battery life (we'll see what Strix brings)
Also both have 16 performance cores, but the Ryzen is faster in multicore. The Ryzen is one year later b/c due to node access/ costs. Doesn't look like "far behind".
There is nothing inherently inefficient about a discrete GPU. Discrete GPUs often have extremely good performance per watt. That's just not the same thing as having a low TDP. Performance per watt is higher when something is twice as power hungry but three times faster.
Not an electrical engineer, my GPU board has lots of additional chips and VRMs, and I do think those should take additional power. All of these are cooled which means they convert power into heat, so I would assume a discrete board draws more power than a SoC. But as I've said, not an electrical engineer (Just some electrical engineering exams at university).
In principle you can shut off anything when it's idle and get its power consumption arbitrarily close to zero.
Discrete GPUs obviously use more power because their use case is when the iGPU isn't fast enough. Hypothetically you can make a discrete GPU with the same performance as an iGPU and it would be no more power hungry. These have occasionally been available, basically monitor cards for CPUs without an iGPU etc. But the ones with a lot of fans and VRMs have them because they do indeed use a lot of power -- which isn't the same as having poor performance per watt, because they're also really fast.
Do you have benchmarks though? TDP is a poor metric for comparison because it varies significantly by manufacturer and doesn’t encapsulate the performance curve at all.
Sorry, I dropped a few words accidentally before submitting and it’s too late to edit it :-( my bad.
I meant to ask for benchmarks across the power spectrum (measured by actual pull not OEM TDP) and off charger. That’s where the x86 processors down clock heavily to keep power in check, and M series pulls ahead because it doesn’t follow suite.
The M series, even at launch, weren’t the king of outright perf, but they were for power to perf.
The M series at launch was already on TSMC 5nm when nothing else was yet.
The problem with asking for benchmarks that actually measure power draw is that somebody would have had to have done them, which hardly anybody does, and specifically on the few CPU models that were made on the same process. So if that's what you want to see, where are yours? Find a comparison that actually measures power draw between two CPUs with similar performance/TDP on the same process, like the M1 Ultra and the Ryzen 7945HX3D.
> That’s where the x86 processors down clock heavily to keep power in check, and M series pulls ahead because it doesn’t follow suite.
That's not really how either of them work. CPUs from any vendor will run at lower clocks under threaded workloads in order to meet their power budget. This is also why the high core count CPUs actually have the best performance per watt -- the cores are clocked lower which is more efficient but you still get the performance from having more of them. And then "race to sleep" etc.
Sounds interesting, do you have numbers - s I get this argument often, that on the same node, Apple is so much better.