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I suspect that apps that use system services might take time to register each app in the appropriate places at startup.

Is the boot time of an iOS device affected by the apps that are running at the previous shutdown or the number of apps installed?

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Are you looking for a philosophical - is it possible that there is some overhead to restore the previous state or a more pragmatic - how does this overhead compare to the entire boot time? My limited evidence is that this is too small to measure, but obviously the number of apps installed increases the springboard load time some number of clock cycles that would need a tool like instruments to actually measure. – bmike Mar 20 '12 at 14:01
Better to edit this question to stand alone than depend on comments that could get deleted on a question that also could go away. I'm not sure what you want me to do - it looks like Kyle is asking you to avoid complicating that question - not saying you have a fully formed question ready to ask... – bmike Mar 20 '12 at 14:32
up vote 2 down vote accepted

My experience is no one, ten or even 50 apps can slow down your boot in any measurable manner. Even an old iPhone 3 with 11 pages of apps booted in visually the same time as a freshly restored iPhone 3.

The reason for this is a number of design choices that provide real benefits to the running system and also are good at isolating boot times from application influences. Specifically, nothing auto-launches, there are not multiple user accounts to prepare, and the OS systems that display and interact with apps work from databases that update when apps are deleted or installed - not at boot time.

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No, during boot of an iOS device only a couple of default applications (springboard, wifi, mobile etc., which could be better called services) are started.

I suspect that apps that use system services might take time to register each app in the appropriate places at startup.

This app are already registered. Let's think of using the push notification service (PNS). During startup of the app they are registering (and renew their registration) to iOS. If you manually close one of this apps or reboot the whole device, the apps is closed, not running and doesn't use any system resources (beside their permanent storage).

If one of this apps is notified by the PNS (or the local notification service), you get a iOS (not app specific) notification and if you then open the app, a special (pre-defined) method

(void)application:(UIApplication *)application didReceiveRemoteNotification

is called and the developer can decide how to handle this kind of event. If you dismiss the notification, the app is not executed.

As bmike wrote, the springboard load time depends of course on the number of installed apps, but I agree that this is small. Also in this this scenario the apps are actually not executed.

To summarize this:

  • Number of apps installed influence the boot time only marginal (see @bmike)
  • App which are running at the previous shutdown does not influence the boot time.
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I have an iPad 1st gen with over 600 apps loaded. It doesn't take longer than the time posted at What's the startup/reboot time for iPad (3rd generation) compared to other iOS devices? to boot up, so I don't believe the number of apps installed matters for boot up. It does matter for checking for updates in the app store, which can take some time.

I've rebooted it after a few weeks of using it with dozens of apps seemingly "open" and I've rebooted it twice in a row, and the reboot time doesn't seem to be different between the two, so the number of open or running apps does not appear to affect boot up.

I've also recently removed the largest of the apps and a few hundred I was no longer interested in to see if I could be happy with a 16GB iPad (3rd gen). Boot up does not seem any different in this case as well.

This is with iOS 5, on a first generation iPad.

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As with all computing the more the device has to load up the more time it will take.

He difference in this case will be minimal as the total storage space of a device is fairly small and the amount of processing power taken up by the applications is also small in comparison to a computer starting up. So will not really notice a difference.

Often iOS updates have included performance upgrades and these updates can reduce login time as the processes are shortened.

The case with apps running at last shutdown is dependable. When you Shut down the device totally the phone has to load up the last pages and instances the apps were in. This again is not an awful lot of processing power and will affect your start-up in seconds.

Advice is to keep multi-tasking apps to a minimum, as they can slow down your device overall, not just booting.

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