What does «sustained performance» mean?

[macddy]

In gaming, what are som examples of sustained performance?

The air doesn’t do fan, but the mbp does. Apple VPs states the mbp will have «higher sustained performance», however the other vp person said they both will be able to run games/pro apps very well.

does sustained perf. mean you wont see an fps drop as quick? Does it mean you can run higher graphics?

would the air without fan just shut down if it got too high? They said the air would under heavy load decrease in performance after a while, any examples on what this means exactly?

 

[Admiral]

Air has no fan, and M1 has a thermal envelope of 10 watts. That's an amount of heat which can be dissipated passively through the case if it is reached in short bursts, which is the case in normal productivity use, but in activities where the CPU is cranking away continuously (video encoding, for example), it would reach 10 watts and stay therefor several minutes or hours. In that case, the CPU may need to throttle to keep heat under control.

 

[macddy]

Air has no fan, and M1 has a thermal envelope of 10 watts. That's an amount of heat which can be dissipated passively through the case if it is reached in short bursts, which is the case in normal productivity use, but in activities where the CPU is cranking away continuously (video encoding, for example), it would reach 10 watts and stay therefor several minutes or hours. In that case, the CPU may need to throttle to keep heat under control.

And how does that look like «live» when the CPU throttles to keep heat under control? What can a user expect to notice when that happens?

 

[Erehy Dobon]

It really depends on the specific application.

My guess is that the M1 in the fanless MacBook Air will be able to maintain peak boost performance only for a couple of minutes before thermal throttling will reduce performance and the system runs at a lower sustained plateau.

For the MacBook Pro and Mac mini -- both of which have active heat dissipation (a.k.a. "fans") -- those systems will be able to maintain higher loads at an extended period, basically a higher plateau.

This is no different from Windows PC hardware.

This is also why Geekbench is a highly derided benchmark since it doesn't capture performance under sustained loads.

 

[Erehy Dobon]

And how does that look like «live» when the CPU throttles to keep heat under control? What can a user expect to notice when that happens?

If you were running a Handbrake encode, it might manifest itself as an encode with an estimated remaining time of 50 minutes all of a sudden jumping to 140 minutes after two minutes.

In the case of the discontinued fanless Intel Retina MacBook 12", it also meant a super sluggish user interface.

 

[AppleFeller]

If you were running a Handbrake encode, it might manifest itself as an encode with an estimated remaining time of 50 minutes all of a sudden jumping to 140 minutes after two minutes.

In the case of the discontinued fanless Intel Retina MacBook 12", it also meant a super sluggish user interface.

2018 MacBook Air here, can confirm interface sluggish, loading anything basically is a waiting game with larger programs or files freezing the system up while it struggles to open them. Was a no brainer to order the Pro to replace this by far underwhelming machine.

 

[Admiral]

And how does that look like «live» when the CPU throttles to keep heat under control? What can a user expect to notice when that happens?

It's a good question, isn't it? I don't think we have any insight into that yet — or at least I haven't. I've never put an iPad under any kind of sustained load which would comparably stress the processor.

However, I expect it would be nearly imperceptible, really, inasmuch as thermal throttling simply means the CPU automatically reduces its utilization — say, from 10W to 7W — for a few minutes until the CPU temperature falls to the point that the throttling profile allows "burst" to maximum speed again.

When the 2015 12" MacBook was throttled its interface would become quite laggy. However, the Apple silicon processors have been designed specifically for a thermally-constrained environment.

 

[leman]

In gaming, what are som examples of sustained performance?

In gaming? Just running a game

Sustained performance is about executing a demanding workload (such as running a game) over prolonged period of time. As you correctly point out, this would make the chip run as fast as it can, pushing it’s to it thermal limits. As the Air is passively cooled, it’s performance dealing will be lower. Basically, what this mean is that Air will be slower in games than a Pro or a Mini.

For the sake of completeness, sustained performance is contrasted with burst performance, e.g. opening an app or compressing a small file. These operation demand high performance from the system and will produce heat, but since they are short, they won’t saturate the thermal capacity of the system, letting the chip perform faster for few seconds than it could if you continue pushing it.

 

[leman]

And how does that look like «live» when the CPU throttles to keep heat under control? What can a user expect to notice when that happens?

Not much I suppose. We are really talking about 30 seconds or so max. If you are playing a game, the FPS has probably already settled at the sustained level by the time you are past the loading screen.

Important thing to note is that “throttling” doesn’t imply that your machine gets laggy abs slow. It’s just that your machine supports a certain performance level and you get a short burst of performance behind that level for the first couple of seconds.