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headlessmike

macrumors 65816
May 16, 2017
1,291
2,582
Does anyone know if a MBA/MBP with M4 will run hotter or cooler? Especially the MBA, I think the M2 was a bit hotter than the M1, and the M3 was a bit hotter than the M2. Which makes sense since it's a more powerful chip and no active cooling. But is this different with the M4? Or will the MBA soon be too hot if Apple creates more powerful chips every year?
It's difficult to say since the iPad Pro has been redesigned since the M2 and never used the M3. None of the Apple Silicon MacBooks Airs have any systematic overheating issues and are designed to run at full power up to at least 100 °C (212 °F), it's just that Apple has been able to increasingly push the performance of the chips within the thermal budget they have. So, the M4 might run hotter (or might not) but there's nothing wrong with that if it works as designed.

M1 users (myself included) are a bit spoiled with low temperatures (my M1 mini never goes above 40 °C) but that just means that Apple was overly conservative with the clock speeds on those chips.
 

Melbourne Park

macrumors 6502a
With TV OLEDs, LG have substantially increased their brightness over the last several years. At the same time, all their TVs have had inconsequential burn in issues. Since 2017, it seems a constant improvement. Samsung introduced a blue light OLED a few years ago, which was brighter due to
...

M1 users (myself included) are a bit spoiled with low temperatures (my M1 mini never goes above 40 °C) but that just means that Apple was overly conservative with the clock speeds on those chips.

IMO higher clock speeds means more heat, which wastes batteries. While slower clock speeds means more time, IMO the iPad pro should not be optimised for performance. It should be optimised for battery life. At the end of the day, its very inconvenient to run out of battery. Plus doing so would not help the battery. Apple should have increased the battery life of the M4 iPad by slowing down the chip and focusing on battery life. For those "pros" who want to run big apps quickly - then get a 13" and have that form factor optimised for speed. And add a larger battery than the iPad 13" is now getting to compensate for the higher clock rate.

Apple don't seem to know what to focus on. There is a difference in usage between a 11" and a 13". Wake up Apple. Battery life counts. As Apple proclaims with its notebooks ...

And finally, I reckon the reason why Apple has not focused on battery life with the new iPads, is because Apple wants the batteries to fail, as soon as possible. Which forces people to buy another unit, because Apple refuses to replace batteries in older iPads. It's ironic that Apple users with failed batteries in iPad Pros - say the 10.5 " one - cannot get their batteries replaced. Yet if Apple would do so, then users would keep their iPads. Which demonstrates that for many, speed is not critical in iPads.
 

headlessmike

macrumors 65816
May 16, 2017
1,291
2,582
With TV OLEDs, LG have substantially increased their brightness over the last several years. At the same time, all their TVs have had inconsequential burn in issues. Since 2017, it seems a constant improvement. Samsung introduced a blue light OLED a few years ago, which was brighter due to


IMO higher clock speeds means more heat, which wastes batteries. While slower clock speeds means more time, IMO the iPad pro should not be optimised for performance. It should be optimised for battery life. At the end of the day, its very inconvenient to run out of battery. Plus doing so would not help the battery. Apple should have increased the battery life of the M4 iPad by slowing down the chip and focusing on battery life. For those "pros" who want to run big apps quickly - then get a 13" and have that form factor optimised for speed. And add a larger battery than the iPad 13" is now getting to compensate for the higher clock rate.

Apple don't seem to know what to focus on. There is a difference in usage between a 11" and a 13". Wake up Apple. Battery life counts. As Apple proclaims with its notebooks ...

And finally, I reckon the reason why Apple has not focused on battery life with the new iPads, is because Apple wants the batteries to fail, as soon as possible. Which forces people to buy another unit, because Apple refuses to replace batteries in older iPads. It's ironic that Apple users with failed batteries in iPad Pros - say the 10.5 " one - cannot get their batteries replaced. Yet if Apple would do so, then users would keep their iPads. Which demonstrates that for many, speed is not critical in iPads.
I was referring to the chips in general and not just in iPads (responding to a question about the M4 in Macs). The reported clock speeds are just the maximum that they can run at and the chips will scale that speed depending on need and thermal loads. Some iPads also explicitly use under clocked chips (the A15 in the iPad mini for example). Apple could have also increased the battery life by making the iPad thicker and using larger cells, although they have apparently increased the battery capacity in the new iPad Pros compared to the last generation despite making them thinner. They have the 10 hour run time as their target and are designin the iPads around that.

As for getting a battery replacement. I can book an appointment to replace the battery in my 10.5" iPad Pro at my local Apple Store this afternoon if I like (I just checked). Not sure where you got the idea that they don't replace batteries from?
 

EugW

macrumors G5
Jun 18, 2017
14,083
11,847
As for getting a battery replacement. I can book an appointment to replace the battery in my 10.5" iPad Pro at my local Apple Store this afternoon if I like (I just checked). Not sure where you got the idea that they don't replace batteries from?
Dunno about the iPad Pro 10.5, but I couldn't get the battery for my iPad Air 2 replaced several years back. I booked an appointment and went to a physical Apple Store. They confirmed that the iPad Air 2 was eligible, both because the battery had degraded sufficiently to qualify, and because the iPad Air 2 still was part of the battery replacement program.

However, they still wouldn't do it because they couldn't order the part. Apple Canada simply did not have it, and wasn't getting any more. What's the point of the battery program if even Apple doesn't have the parts? Their only suggestion was for me to call third party authorized Apple repair shops. So I did, and those shops said that was pointless because they order the parts from Apple too of course.

I suspect the problem in this case was that the device was in the last year of its eligibility. By that time, perhaps it's not uncommon for the parts to no longer exist.
 

magbarn

macrumors 68030
Oct 25, 2008
2,970
2,274
I was referring to the chips in general and not just in iPads (responding to a question about the M4 in Macs). The reported clock speeds are just the maximum that they can run at and the chips will scale that speed depending on need and thermal loads. Some iPads also explicitly use under clocked chips (the A15 in the iPad mini for example). Apple could have also increased the battery life by making the iPad thicker and using larger cells, although they have apparently increased the battery capacity in the new iPad Pros compared to the last generation despite making them thinner. They have the 10 hour run time as their target and are designin the iPads around that.

As for getting a battery replacement. I can book an appointment to replace the battery in my 10.5" iPad Pro at my local Apple Store this afternoon if I like (I just checked). Not sure where you got the idea that they don't replace batteries from?
Sounds like you haven't ever tried getting your iPad batteries replaced. Both my Air 2 and 10.5 iPP have less than 80% battery life according to coconut battery, last only 1-2 hours per charge and Apple flat out refuses to replace the batteries.
Their stupid "diagnostic" app always claims healthy batteries despite their poor battery life vs. when new.
I've had multiple Apple Store trips with wasted time and arguing with multiple "geniuses" to no avail.
Quick google search shows I'm not alone in this.
 
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Confused-User

macrumors 6502a
Oct 14, 2014
584
625
I’m not sure of the actual ratios or whatever but let’s say we rate power 1 to 10 and brightness 1 to 10 as well. Since power vs brightness isn’t linear, let’s say on average to reach brightness 5 you need power 3 but to reach brightness 10 you need to have power 10.

Single layer:
Pixel 1 - brightness 10, power 10
Really bad for pixel 1 longevity

Dual layer ideal with 2 equally sensitive pixels:
Pixel 1 - brightness 5, power 3
Pixel 2 - brightness 5, power 3
Very safe for pixel 1 & 2 longevity

Dual layer with one less sensitive pixel (not balanced for power):
Pixel 1 - brightness 5, power 6
Pixel 2 - brightness 5, power 3
Not good for Pixel 1 longevity
Very safe for Pixel 2 longevity

Dual layer with one less sensitive pixel (rebalanced for power):
Pixel 1 - brightness 4, power 4.5
Pixel 2 - brightness 6, power 4.5
Reasonably safe for both Pixel 1 & 2 longevity

These numbers are made up, but I hope it does illustrate how rebalancing between two pixels of different sensitivities can help.
Thank you, but I understood all that. It doesn't address my questions.

1) In your last scenario, how does it know to crank the power to 4.5? It would need a sensor, somewhere, to tell it to drive that pixel more than normal. That's what I meant by asking about calibration.

2) In your third scenario... well, I don't believe that's possible with the technology they're using, since both pixels are driven by a single anode and cathode. However even if it were possible, how would it know to do that? Again you need some sort of calibration.

3) Also in your third scenario, you would get unbalanced degradation of output over time, since you'd be driving one layer of that pixel a lot harder than the other. That would need to be tracked, and you'd need to have a really idea of the performance curve over time, which may be impossible to know early in the lifetime of that panel technology. Or else you'd need, again, ongoing calibration while deployed.

To reiterate a point from question #2 above - I believe the tech in use only allows for both layers to have the same power at all times. This simplifies things a lot, and I think it implies that the only possible answer is that they do factory calibration. ...unless, hm, maybe they can test resistance on each pixel while in use, over time, and draw conclusions about the pixel from that? I'm way out in the weeds on this though. No idea really.

Does anyone know if a MBA/MBP with M4 will run hotter or cooler? Especially the MBA, I think the M2 was a bit hotter than the M1, and the M3 was a bit hotter than the M2. Which makes sense since it's a more powerful chip and no active cooling. But is this different with the M4? Or will the MBA soon be too hot if Apple creates more powerful chips every year?
Expect the MBA to be comfortable to hold. Expect the MBP to be comfortable to hold. Beyond that, details will be chosen by Apple to optimize for battery and performance according to details only they know.

It is silly to imagine the MBA getting too hot. That is a large part of why they left Intel. They're not going to do the same thing.

Dunno about the iPad Pro 10.5, but I couldn't get the battery for my iPad Air 2 replaced several years back. I booked an appointment and went to a physical Apple Store. They confirmed that the iPad Air 2 was eligible, both because the battery had degraded sufficiently to qualify, and because the iPad Air 2 still was part of the battery replacement program.

However, they still wouldn't do it because they couldn't order the part. Apple Canada simply did not have it, and wasn't getting any more. What's the point of the battery program if even Apple doesn't have the parts? Their only suggestion was for me to call third party authorized Apple repair shops. So I did, and those shops said that was pointless because they order the parts from Apple too of course.

I suspect the problem in this case was that the device was in the last year of its eligibility. By that time, perhaps it's not uncommon for the parts to no longer exist.
That's pretty unusual. I think a complaint to Apple Corporate would have probably produced results, not that you should have to do that. Their policy in such cases is to replace with a refurbished newer unit. So for example recently they replaced my Apple Watch 4 with an Apple Watch 5 because they no longer had a replacement battery available. No charge aside from the battery swap fee.
 
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Confused-User

macrumors 6502a
Oct 14, 2014
584
625
IMO higher clock speeds means more heat, which wastes batteries. While slower clock speeds means more time, IMO the iPad pro should not be optimised for performance. [blah blah blah]
Apple don't seem to know what to focus on. There is a difference in usage between a 11" and a 13". Wake up Apple. Battery life counts. As Apple proclaims with its notebooks ...
Apple is clearly focusing on performance with the Pro line. Thus the use of M4, and other best-in-class chips in previous gens. You don't like it, fine, there are other pads available for you. "Wake up Apple" just makes you sound ridiculous.
And finally, I reckon the reason why Apple has not focused on battery life with the new iPads, is because Apple wants the batteries to fail, as soon as possible. [blah blah blah]
You should probably get a chin strap for that tin foil hat of yours.
 

EugW

macrumors G5
Jun 18, 2017
14,083
11,847
Thank you, but I understood all that. It doesn't address my questions.

1) In your last scenario, how does it know to crank the power to 4.5? It would need a sensor, somewhere, to tell it to drive that pixel more than normal. That's what I meant by asking about calibration.

2) In your third scenario... well, I don't believe that's possible with the technology they're using, since both pixels are driven by a single anode and cathode. However even if it were possible, how would it know to do that? Again you need some sort of calibration.

3) Also in your third scenario, you would get unbalanced degradation of output over time, since you'd be driving one layer of that pixel a lot harder than the other. That would need to be tracked, and you'd need to have a really idea of the performance curve over time, which may be impossible to know early in the lifetime of that panel technology. Or else you'd need, again, ongoing calibration while deployed.

To reiterate a point from question #2 above - I believe the tech in use only allows for both layers to have the same power at all times. This simplifies things a lot, and I think it implies that the only possible answer is that they do factory calibration. ...unless, hm, maybe they can test resistance on each pixel while in use, over time, and draw conclusions about the pixel from that? I'm way out in the weeds on this though. No idea really.
To be honest, I don't know how the calibration is done, as I am not an engineer. However, I would not be surprised if it is a one-time in-factory calibration, and that there will be inconsistent pixel fading over time. Still, even if true, that inconsistent fading would be significantly less than with single-layer OLED designs, since each pixel from a dual-layer design would be running at significantly lower power levels than would be required with a single-layer design.

However, each pixel is indeed individually controlled for brightness by varying power levels to each individual pixel. There is an electrical grid on which these pixels are placed, so a 4K monitor would have 3840 vertical traces and 2160 horizontal traces. Where these thousands of traces cross is where is each of the 8.3 million individual pixels is located, and each of those are individually controlled. For dual layer, I'm not sure how each pixel pair is controlled, but even if they are controlled as a pair that has been previously calibrated, that would still serve to reduce wear over time.

BTW, for that 3rd scenario (not balanced for power), that was my example of what you might not want to do. What could be better is the 4th scenario (rebalanced for power), or else somewhere in between scenario 3 and scenario 4 that works best under their testing.
 
Last edited:

Confused-User

macrumors 6502a
Oct 14, 2014
584
625
To be honest, I don't know how the calibration is done, as I am not an engineer. However, I would not be surprised if it is a one-time in-factory calibration, and that there will be inconsistent pixel fading over time. Still, even if true, that inconsistent fading would be significantly less than with single-layer OLED designs, since each pixel from a dual-layer design would be running at significantly lower power levels than would be required with a single-layer design.
But this is the interesting question. So I hope someone can produce an answer.

However, each pixel is indeed individually controlled [etc., we all know how LEDs work]. For dual layer, I'm not sure how each pixel pair is controlled, but even if they are controlled as a pair that has been previously calibrated, that would still serve to reduce wear over time.
I *am* sure, and I just explained it. There is a single anode/cathode pair for each pixel. A single source of power from which both LEDs (subpixels, really) draw. There was a nice diagram of the layout posted here somewhere a day or two ago - maybe even in this thread - but I can't put my hands on it at this moment.

And yes, you're right, this still improves the wear profile due to lower maximum power. What it doesn't do is eliminate pixel variance due to overdriving one of the two layers, which is a claim I've seen a few times here. And it still assumes calibration, which I'd still like to understand better - is a per-subpixel profile generated at the factory and loaded into each device?
 

EugW

macrumors G5
Jun 18, 2017
14,083
11,847
What it doesn't do is eliminate pixel variance due to overdriving one of the two layers, which is a claim I've seen a few times here.
It would not eliminate pixel variance, but as you say, it would slow it down.

And perhaps it would effectively almost eliminate it for the vast majority of users in say a 5 year time frame... We can hope, and we shall see.

In my case, I'm not too concerned, but I do not typically run at near full brightness.
 

theotherphil

macrumors 6502a
Sep 21, 2012
898
1,222
Games, running workloads faster so that the machine can go to sleep faster to save battery life.

Faster processing (at same/similar power draw) is always better to have, especially in a battery powered device.
As you said, the race to sleep, along with more efficiency has allowed a thinner device and a smaller battery for the same run time.

This then leads to weight savings.

The only way to enable that form factor with better performance than previous generations, was with M4.
 
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Jacquesass

macrumors regular
May 6, 2003
212
41
I have an iPad Pro 11" 2nd gen (released March 2020). Just ran Geekbench 6 and got:

CPU single= 1355, CPU multi = 4748, GPU=18979.

That is very close to a 3x (!) improvement in 4 years. That's insane.
 
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johannnn

macrumors 68020
Nov 20, 2009
2,228
2,346
Sweden
Expect the MBA to be comfortable to hold. Expect the MBP to be comfortable to hold. Beyond that, details will be chosen by Apple to optimize for battery and performance according to details only they know.

It is silly to imagine the MBA getting too hot. That is a large part of why they left Intel. They're not going to do the same thing.
What I mean is, if the chip is getting a bit hotter for each generation, that means the MBA will throttle a bit more for each generation because of no active cooling. I felt that my M1 Air never throttles because it never gets warm. If the M4 Air is a bit warmer, and can get much warmer during heavy load, that might convince some of us to go for the M4 Pro instead.
 

Confused-User

macrumors 6502a
Oct 14, 2014
584
625
What I mean is, if the chip is getting a bit hotter for each generation, that means the MBA will throttle a bit more for each generation because of no active cooling. I felt that my M1 Air never throttles because it never gets warm. If the M4 Air is a bit warmer, and can get much warmer during heavy load, that might convince some of us to go for the M4 Pro instead.
Your premises are incorrect, because you misunderstand how chips work and the notion of "throttling".

It seems that many people think that chips have a natural speed, and that when they get too hot to run at that speed, you have to throttle them. But that's false.

All chips have a characteristic power-performance curve. If you run the chip very slowly, at one end of the curve, you'll generate very little heat. As you ramp up the speed of the chip, it run hotter and hotter. The curve usually extends (almost?) all the way down to zero (no performance at all) but it does not extend out to infinity - you can't run it infinitely fast even if you can cool it with infinite efficiency, because certain design choices you make will limit the maximum speed, regardless of temperatures and voltages. Also, power and performance don't scale linearly: in the general case, every time you ratchet up performance, it costs more power than the previous same-size performance increase.

Every chip's curve is different, and it defines what the optimal speed range is for that chip. That is, mostly, you want to run as fast as you can given:
- you're not using power inefficiently. You mostly want to stick close-ish to the part of the curve where power and performance *do* scale close to linearly. (Unless you're Intel...)
- you're not exceeding the heat envelope of the device the chip is in.
- you're not using more power than is available (either instantaneously, usually not an issue, or over time, due to battery constraints).

So, coming back to your example: Your M1 Air *does* "throttle". It does so aggressively enough that it never feels warm to you. (In fact, with chosen loads, you can get it to run warm. You can't get it to run really hot though.) But that's not really a property of the chip, it's a property of the choices Apple made in the part of the OS that manages CPU utilization. They certainly could run it hot, if they wanted to.

Changes from generation to generation that you perceive - that the M2 and M3 "run hotter" - are not properties of the chips themselves. They are, just as with the M1, properties of the choices Apple made for them: what kind of device to put them in, and how hot to allow those devices to get. Apple decided to get a little more aggressive with the M2 and the M3 in the MBAs, allowing them to run faster and draw more energy for longer than they did the M1.

To put it another way: The M3 is strictly more efficient than the M2, which is strictly more efficient than the M1. That means that for any level of performance that you care to pick, the M3 will always run cooler than the M2, which in turn will always run cooler than the M1. The reason MBAs with newer chips are running a little hotter is that they're not running the same level of performance- they're running faster. In fact their performance increase outstrips their efficiency increase a bit, but they did in fact get more efficient too.

All of this continues with the M4. So how it behaves in the MBA and the MBP will depend solely on Apple's choices about how hot and how fast they want those devices to run. You can't predict those choices based on the properties of the chip that we can discern in the iPad.

TL;DR: You can't know if the M4 MBA will "run hot" or not based on what you know now.
 

nappes

macrumors member
Sep 9, 2016
54
81
With TV OLEDs, LG have substantially increased their brightness over the last several years. At the same time, all their TVs have had inconsequential burn in issues. Since 2017, it seems a constant improvement. Samsung introduced a blue light OLED a few years ago, which was brighter due to


IMO higher clock speeds means more heat, which wastes batteries. While slower clock speeds means more time, IMO the iPad pro should not be optimised for performance. It should be optimised for battery life. At the end of the day, its very inconvenient to run out of battery. Plus doing so would not help the battery. Apple should have increased the battery life of the M4 iPad by slowing down the chip and focusing on battery life. For those "pros" who want to run big apps quickly - then get a 13" and have that form factor optimised for speed. And add a larger battery than the iPad 13" is now getting to compensate for the higher clock rate.

Apple don't seem to know what to focus on. There is a difference in usage between a 11" and a 13". Wake up Apple. Battery life counts. As Apple proclaims with its notebooks ...

And finally, I reckon the reason why Apple has not focused on battery life with the new iPads, is because Apple wants the batteries to fail, as soon as possible. Which forces people to buy another unit, because Apple refuses to replace batteries in older iPads. It's ironic that Apple users with failed batteries in iPad Pros - say the 10.5 " one - cannot get their batteries replaced. Yet if Apple would do so, then users would keep their iPads. Which demonstrates that for many, speed is not critical in iPads.

You know you can just turn on low power mode right if you want to optimize for battery life?

also look up “race to sleep” sometimes being faster can save battery. Not just the cpu actaullly, the quicker a user finishes a task the quicker the screen can dim and the cellular / WiFi radio can turn off as well
 

magbarn

macrumors 68030
Oct 25, 2008
2,970
2,274
They have never done this. Come up with facts before making baseless statements like these.

If you are referring to the battery power limit for old batteries: Apple limited the power draw of devices with older batteries, much like electric vehicles limit max performance if a battery is near dead or indeed older. There is nothing nefarious about that: replacing the battery will restore performance or you could choose to just live with it: what good is an iPhone with a 70% capacity and max power if it goes dead in 30m?

For all this complaining ‘modern iPads are OP for multiple generations now’, it is surprising how those same people will moan about supposed ‘slowing down’. 80% of completely overpowered is probably still good enough…

Or put differently, if Apple would have wanted to maliciously kneecap devices to get you to upgrade, they wouldn’t have advertised in their UI.
The nerfing has already started. Look at the 80% charge limiter for the just released ipads that Apple is artificially keeping out of older ipads, particularly the M2 equipped ipad pros.
 

Boing123

macrumors member
Mar 30, 2024
64
58
The nerfing has already started. Look at the 80% charge limiter for the just released ipads that Apple is artificially keeping out of older ipads, particularly the M2 equipped ipad pros.
I’m not so sure: the state of charge is very likely governed by some kind of battery controller. Even when the device is powered off, voltage and charge behavior need to be controlled.

Further support for this hypothesis comes from the fact that e.g. Intel Macs allow apps like Al Dente or similar to control max charge level at any arbitrary level while M1 devises only allow two options 100 or 80 (see e.g. https://github.com/zackelia/bclm)

Contrary to your iPad example, for MacBooks, the newer devices are more limited than the older ones.

Therefore, it is perfectly possible the combination of asic on the battery controller, the firmware and other factors contribute to this feature not being backward compatible with older devices.

Nothing evil, nothing deliberate.

Also, limiting the state of charge is more useful on a _new_ battery. An older one is already degraded so why bother…
 

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NT1440

macrumors G5
May 18, 2008
14,756
21,449
I’m not so sure: the state of charge is very likely governed by some kind of battery controller. Even when the device is powered off, voltage and charge behavior need to be controlled.

Further support for this hypothesis comes from the fact that e.g. Intel Macs allow apps like Al Dente or similar to control max charge level at any arbitrary level while M1 devises only allow two options 100 or 80 (see e.g. https://github.com/zackelia/bclm)

Contrary to your iPad example, for MacBooks, the newer devices are more limited than the older ones.

Therefore, it is perfectly possible the combination of asic on the battery controller, the firmware and other factors contribute to this feature not being backward compatible with older devices.

Nothing evil, nothing deliberate.

Also, limiting the state of charge is more useful on a _new_ battery. An older one is already degraded so why bother…
No no no. Everything Apple does is for purely evil reasons. There is no room for actual hardware design, limitations, or other technical information here, this is MR!

All kidding aside, the idea that you responded to of *any* rational person buying a new iPad because they can now monitor and manage the battery is just…wow.

I miss the old Chipworks days where you could get extremely detailed and useful analysis of the A series chips down examination of how the 3rd party controllers work. Unfortunately that kind of stuff is now locked behind paywalls where only a corporate subscription (Thousands of dollars) will get you access. I’d love to know if Apple has started developing their own lesser-headline-grabbing chips like battery controllers.
 
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bousozoku

Moderator emeritus
Jun 25, 2002
15,929
2,146
Lard
Can’t wait to see what M4 max and Ultra can do. Can Apple put an ultra in 16 MBP. Apple should put M4 in AVP 2.
It would be interesting to see what Apple could do if they started a new line with proper heat dissipation for gaming. If Razer can put a proper 14 inch machine together, certainly Apple could.
 

magbarn

macrumors 68030
Oct 25, 2008
2,970
2,274
I’m not so sure: the state of charge is very likely governed by some kind of battery controller. Even when the device is powered off, voltage and charge behavior need to be controlled.

Further support for this hypothesis comes from the fact that e.g. Intel Macs allow apps like Al Dente or similar to control max charge level at any arbitrary level while M1 devises only allow two options 100 or 80 (see e.g. https://github.com/zackelia/bclm)

Contrary to your iPad example, for MacBooks, the newer devices are more limited than the older ones.

Therefore, it is perfectly possible the combination of asic on the battery controller, the firmware and other factors contribute to this feature not being backward compatible with older devices.

Nothing evil, nothing deliberate.

Also, limiting the state of charge is more useful on a _new_ battery. An older one is already degraded so why bother…
Every lithium battery charger has charge limiter based on voltage for safety reasons. Voltage max adjustments have also been a feature of lithium battery controllers for years. It’s just a setting that Apple chooses to lock from the end user. Lithium batteries state of charge is determined by voltage and it’s very simple to adjust. Hardware should be able to do it. Likely Apple being too lazy to allow it on older devices. But both of us will never truly know unless you know an Apple engineer.
 

EugW

macrumors G5
Jun 18, 2017
14,083
11,847
Achievement unlocked!

M4 9-core has breached the GB 4000 barrier.


View attachment 2378311
BTW, I got the info from this post by amosliu137 over at AnandTech who saw the original Weibo post here.

It involved liquid nitrogen:

iPadProM4_LiquidNitrogen.jpeg


With that, this fanless iPad has reached the leaderboard front page for fastest single-core in Geekbench 6.

Geekbench 6 Results - Geekbench.jpg


Also, that 13595 multi-core score is the fastest so far for the M4 9-core. The fastest M4 10-core score so far (apparently achieved in a freezer) is 14924, which is <10% faster.
 
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