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MacRumors

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Original poster
Apr 12, 2001
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In iOS 9, some of the best features are the ones that aren't readily visible. iOS 9 has several under-the-hood updates that boost battery life, improve security, and cut down on the amount of storage space iOS updates and apps use on iPhones and iPads.

Even disregarding all of the consumer facing features, these quiet improvements make the upgrade to iOS 9 from iOS 8 or iOS 7 well worth it on all supported devices: the iPhone 4s and up, the iPad 2 and up, and all iPad mini models.

Battery Life

With operating system optimizations, Apple is able to eke out an additional hour of battery life on iPhones under normal usage conditions. One of these improvements, for example, pertains to the iPhone's ambient light and proximity sensor. When the iPhone is placed facedown, it now detects that the screen isn't visible, so an incoming notification does not light up the screen.

batterysettings.jpg

There's also a new Low Power Mode on the iPhone that can add another three hours of battery life by cutting down on battery-draining features. Low Power Mode turns off automatic Mail fetch, disables background app refresh, disables motion effects, and disables animated wallpapers.

Low Power mode also throttles the performance of the iPhone so it drains less power. Benchmark testing suggests Low Power mode reduces an iPhone's performance by about 40 percent to cut down on power usage.

Security

iOS 9 prompts users to create 6-digit passcodes instead of 4-digit passcodes for additional security. It's still possible to create a 4-digit passcode, but Apple recommends a 6-digit code because it adds one million possible combinations instead of 10,000, making a passcode harder to crack. Two-factor authentication support is also enhanced in iOS 9.

ios9security-800x486.jpg

Installation Size

With iOS 9, Apple's cut way down on the installation size, so far less free space is required to download the new update. While iOS required 4.58 GB of space to install, iOS 9 requires only 1.3 GB of space to install, making it more accessible to users who have 16 GB iOS devices.

appdeletionstuff.jpg

For devices that still don't have enough space to install the iOS 9 update, Apple has a new auto app delete/reinstall feature. When attempting to install iOS 9 on a device with insufficient space, there's a popup that offers to temporarily delete some apps in order to make room for the update. Apps that are deleted are then reinstalled and replaced after the operating system update is completed.

App Thinning

Apps from third-party developers also require less installation space thanks to a feature called App Thinning. With App Thinning, apps can be optimized for specific devices, allowing them to take up less space on iOS devices.

An app for the iPhone doesn't need all of the iPad assets, so those won't be downloaded. That means faster installs, faster launch times, and more storage space left for other apps and content.

App Thinning also includes on-demand resources like image and sound files, which can be downloaded only when needed. The imagery for later levels in a game, for example, might not be downloaded until it's necessary.

Metal

Apps in iOS 9 take advantage of Metal, making more efficient use of the CPU and GPU for faster scrolling, smoother animations, and better performance. Email, messages, web pages, and PDFs all render faster.

Article Link: Inside iOS 9: Under-the-Hood Improvements for Battery Life, Security, and More
 

Mr. Donahue

macrumors 6502
Sep 17, 2014
495
671
I'm still waiting for an update to apple music. So many little bugs. Issues.

I'm also waiting for the day I can add photos to any photo album even if I uploaded the photo album from my MacBook to iPhone I still want to be able to make changes and add to and delete.
 
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Mackker

macrumors member
May 22, 2015
39
45
iPhone 4S: battery sucks big time (6% lost in almost 5 minutes) and performance without Low power mode enabled is awful!
Why Apple engineers don't design software on less capable devices first and move on from there?
 
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Zwhaler

macrumors 604
Jun 10, 2006
6,945
1,304
Is iOS 9 definitely faster equal or faster on the 4S? It sure wasn't on iOS 8.
edit: the guy above me who posted as I was writing this answered my question.
 
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devinthomas

macrumors regular
Mar 16, 2013
210
235
When does Two-factor authentication roll out? I'm still getting Two-step verification on El Cap GM & iOS 9 public release.
 
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Maleption

macrumors member
Sep 15, 2013
39
42
About tansfer puchase back to iTunes:

How A universal app on iPad with app thinning enabled get transferred back to iTunes? And can we install that IPA to a iPhone?
 
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arkmannj

macrumors 68000
Oct 1, 2003
1,641
401
UT
How's it on the iPhone 5? I was doing the Beta's but a couple weeks ago was fed up with the bugs. (Beta, I didn't blame Apple, but I didn't want the bugs anymore either) Did they get some of the stability and such ironed out?
 
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TMRJIJ

macrumors 68040
Dec 12, 2011
3,272
5,507
South Carolina, United States
iPhone 4S: battery sucks big time (6% lost in almost 5 minutes) and performance without Low power mode enabled is awful!
Why Apple engineers don't design software on less capable devices first and move on from there?
It's the first day and it's indexing. You can complain about it tomorrow but right now we hold your review with a grain of salt.
 
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Mackker

macrumors member
May 22, 2015
39
45
Because then the software will be less capable, and devices newer than the 4S would go to waste.
I disagree. I'm an iOS Developer and I know what these devices are capable of.
That's one. Another thing would be that designing software on less performant devices will lead to great performance advantages for more performant ones. Also, who says that designing software for slower devices will impair new or more features for the faster ones? At its core the software must be fast!
 
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Mackker

macrumors member
May 22, 2015
39
45
It's the first day and it's indexing. You can complain about it tomorrow but right now we hold your review with a grain of salt.
I've been using the iOS 9 GM for a few days. Nothing changed. You can take my review as granted.
As I said in another comment: with Low Power Mode ON, the OS is definitely faster on iPhone 4S. The only "issue" would be that the function gets automatically disabled when the device is charged after a certain threshold (60% I think).
 
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Mr. Donahue

macrumors 6502
Sep 17, 2014
495
671
Also I want to be able to fingerprint ID enabled for purchases but I don't want it enabled for lock screen and I don't want a password ever.
 
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0098386

Suspended
Jan 18, 2005
21,574
2,908
I've been on 9GM for about a week now. I really like it! It's very smooth, and my battery life seems slightly better too. I'd like that emergency battery mode thing to have a control centre shortcut, though.

Love the new font too. Very readable.
 
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postpc

macrumors regular
Sep 3, 2013
158
115
Germany
I've been hard on Apple for the last couple of months, but IOS 9 feels brilliant. No Safari crashes so far, and its snappyness has been taken up or notch, everything feels fast and fluent on my dated Ipad 4. Looks like this could be the long awaited Snow Leopard release.
Well done Apple, credit where credit is due.
 
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Glassed Silver

macrumors 68020
Mar 10, 2007
2,096
2,561
Kassel, Germany
App Thinning also includes on-demand resources like image and sound files, which can be downloaded only when needed. The imagery for later levels in a game, for example, might not be downloaded until it's necessary.

I can't wait for this becoming an issue when abroad and without good data allowance. (if any)

Glassed Silver:mac
 
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Hardingster

macrumors newbie
Jul 10, 2008
3
0
I am not seeing a reduction on the iOS9 installation size. I have a 16 GB iPhone 5. Capacity is showing 12.5 GB after installing iOS9.

Anyone else seeing this?
 
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