4S should disable one core most of the time

Then why have 2?

 

For apps.

 

Apple has stated that the A5 processor uses the same amount of power as the A4, even though it has two cores. I'm thrilled with the battery life of my 4S, and while I understand that some people have issues with it, I do not believe this would be a good solution.

 

When I turn off the iMessage/iCloud features that seem to have my iPhone 4s connecting to 3G data way more than my iPhone 4 did, my iPhone 4s gets slightly better battery life than the iPhone 4. I don't think that's core related.

 

that is not what is causing the bad battery life for people :roll eyes:

 

you should try killing apps that are running in the background. especially location services.

 

That way, you wouldn't get any more battery life.

ARM processors don't give any power to parts of the processor that are not currently in use. There is no need to disable an ARM processor; just don't give it instructions to execute.

When there is some work to do, the most power efficient way to do the work is to use all cores, but at the lowest possible clock rate. Power increases with the square of speed, therefore two cores at half the speed use much less power than one core at full speed.

 

the battery issues are coming from elsewhere

 

You have to consider the speed a processor can get back to sleep vs the power used.

For example if a dual core processor uses 30% more power at 100% usage. But can complete the task 40% faster and get back to sleep then in the end you've used less battery.

Here is a good article that is mostly about the 4s

http://www.anandtech.com/show/4971/apple-iphone-4s-review-att-verizon/15

 

Yes, it's usually most efficient to do the work as fast as possible and screw the battery hit, because then the work is done and the CPU goes back to sleep where it consumes near zero power. And I'm pretty sure the A5 DOES power down one core when it's doing light work. It'd be pretty silly if it kept both active when only one is in use.

 

The apps aren't running in the background. They're suspended or frozen. That's one of the biggest misconceptions about the multitasking tray. Those apps are your recently used apps and are not running. The first screen are the frozen apps and the rest are just the recently used. They're not using up extra battery. Reboot your phone. If those apps were supposed to be still running, they wouldn't be there after a reboot. After a while iOS kills them completely but they still remain in the tray.

 

Calling it the "multitasking tray" further confuses people. It's what you say in your next sentence, it just shows your recently used apps. Which are all 'suspended'.

Though some do still run, i.e. mapquest4mobile (and I'd assume all other navigation apps) and iPod or "music" now I guess just to name a couple.

 

Start up a navigation application and leave it running in the background.

While what you said is mostly true, they can activate system processes that remain active in the background.

JJ

 

This is correct.

App developers can choose to use one of 7 multitasking APIs that are provided by iOS. When using one of these APIs, their own application transfers its processes to iOS' API sub-structure. The app is then frozen until it becomes the active app or it's killed by iOS to free up ram.

 

Exactly. And while the poster above may not have expressed it technically correctly, apps that activate and run those processes in the background can use battery more quickly. Which is why that poster recommended force quitting applications specifically those that use location services... Sigh.

 

X 2. This is exactly what I was going to say.