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Why older iPhones can't multitask in iPhone 4.0

updated 04:05 pm EDT, Thu April 8, 2010

Hardware limits dictate iPhone 4 limits

Apple's unveiling of iPhone 4.0 has already stirred controversy by cutting multitasking for all older iPhone and iPod touch models; some have accused Apple of forcing upgrades. The truth, however, is that there are very real hardware limits that make multitasking impractical. Having experience with multiple platforms, Electronista can explain just why Apple made the hard call to drop the important feature on most of its older devices.

More than anything, multitasking depends most heavily on RAM. An app running in the background will need at least a small slice of memory to keep running. The problem with the iPhone 3G and the second-generation iPod touch (including the 2009 8GB model) is that there simply isn't much. Both only have 128MB to work with, which is low by modern standards and could push some of these devices to the breaking point. Memory-hungry apps like We Rule could take as much as a quarter of the RAM just for themselves; even with the controlled multitasking in iPhone 4.0, it could still take already scarce resources away from basic functions. The iPhone 3GS and latest iPods have 256MB of RAM, and while this won't be perfect, there should be much more headroom.

Processor speed is also a noticeable, if less critical, component. The leap from the iPhone 3G's 412MHz chip to the iPhone 3GS' (and third-run iPod's) 600MHz ARM Cortex-A8 can't be understated: just about every task runs faster with the new architecture and higher clock speed. That already has an impact on the current iPhone OS, but with multitasking, any speed or slowness is magnified: the CPU not only has to handle whatever's running in the foreground but devote a small amount of its time to the background. While the iPhone 3G could likely handle some tasks in the background without fault, others would likely bog it down. At least in theory, newer Apple devices should make that almost unnoticeable.

While we certainly like all features being available to as many phones as possible, we've seen the consequences of what happens with borderline specs when multitasking comes into play. Nokia's N97 has been the most frequently cited example: when it shipped last summer, it was criticized for being too slow for the price precisely because its CPU and RAM -- both very similar to the iPhone 3G -- weren't up to the load the Symbian OS and its apps demanded. The N97 mini and the N900 were virtually rushed out the door as a result.

Android hasn't been immune, either. While most phones are well-equipped, the original T-Mobile G1 and early versions of the HTC Magic had little enough RAM (192MB) and processor speed (a more than year-old 528MHz Qualcomm chip) that they would very noticeably slow down as more apps were left open. It should be telling that the Nexus One and Evo 4G have 512MB and even 1GB of RAM on top of their 1GHz processors; depending on the tasks, it can take that much to guarantee smooth performance in all conditions.

In many ways, the feature cut for older phones was inevitable. Eventually, certain features were simply going to be impossible on older hardware, and Apple had to make a decision to either drop features on some devices or strip them down to where they work everywhere. Given that multitasking is one of the most heavily requested features in the iPhone's brief history, it's not entirely surprising that Apple decided to provide the feature for a few at first. We can only hope that it's as well executed as Apple has promised.

by MacNN Staff



  1. Makosuke

    Joined: Dec 1969


    Nice Summary

    This is a nice, well-reasoned explanation of what is an area people are apt to get worked up about without really thinking through the realities and consequences of what they're asking for. Kudos to MacNN for laying it out clearly and calmly.

    The fact that Apple is offering multitasking at all is a good thing, and I personally support the decision to do it in a way that preserves the fast and smooth feel of iPhone-class devices, even if it means cutting off older ones.

  1. aol

    Joined: Dec 1969


    Not buying what you're selling

    I read the announcement a different way. I read it that there will be seven apis that apps can call (i.e., voip, sound, etc.) and when you "multi-task" what you're really doing is saving app state and allowing that app to call any of those 7 multi-task processes that are already running all the time as services in the OS. I didn't read it that Apple is doing true multi-tasking like they are doing with Safari, mail and springboard (the blessed Apple background apps).

    So you're in Pandora, and you need to Tweet. You double-tap, and Pandora is told "hey the user is putting you to background". The app saves it's state, invokes one ore more of those 7 backgrounding tasks, and quits.

    If RAM is the issue as it may well be, it may be that the addition of those 7 background services is more than the iPhone 2G can handle. But I disagree with how you read the announcement.

  1. joecab

    Joined: Dec 1969


    remember, jailbroken iPhones multitask...

    but there's never going to be a way to know for sure if it's just Apple wanting an optimal experience in using multitasking, or if they're just hoping to force some phone upgrades. One thing for sure is that Apple is going to be a lot pickier about it than a jailbraker. How long do people hold onto their iPhones, anyway? I plan to get a new one every two years like clockwork, just when my old contract expires, so I don't care much about feature cutoff.

  1. Salty

    Joined: Dec 1969



    To be honest it's a fair thing to drop, the phone is more than two years old, anyone who got a 3G when it came out will be able to upgrade, anyone who got it right near the end will only have to wait a year. Anyone who got a 3G this year obviously didn't care about having the latest and greatest.

    I can't really fault Apple for making this only a top tier feature. Besides it inspires all the original iPhone owners to pony up for a new one!

    Comment buried. Show
  1. testudo

    Joined: Dec 1969


    Re: Fair

    I can't really fault Apple for making this only a top tier feature. Besides it inspires all the original iPhone owners to pony up for a new one!

    I guess one person's 'inspiration' is another's 'forced upgrade'.

  1. jamck1977

    Joined: Dec 1969


    My 2G...

    I have a jailbroken/unlocked 2G. I could use apps that multitask, and have tried, but it drained my battery faster (just like having push notifications - which also affected my wife's 3G charge time). What I really want is to not have to jailbreak/unlock every time they update the firmware. My iPhone is well outside the 2 year contract limit, when am I 'free' to go elsewhere without having to jailbreak?

    Don't get me wrong, it was my choice and I don't think anyone should specifically pay attention to me, but you would think that on a firmware update, it could check there serial number and any phone older than 2.5 years could be unlocked with the update...Will this ever happen?

  1. iphonerulez

    Joined: Dec 1969


    Again, it appears that Apple is focusing

    on a good user experience instead of just slapping multitasking on all models. What's the point of multitasking if it practically brings foreground apps to a standstill or causes the OS to crash. The people with the older iPhones and Touches didn't buy it with multitasking, so they'll just have to do without for the rest of the life of the product. It doesn't make the older product obsolete. Apple is always being criticized for cheating users. There have been lots of Android smartphones that were barely a year old that have been left behind by the latest Android OS updates. Is that Google also trying "force upgrade" to newer models? Nobody is being "forced" to do anything of the sort. If people feel they want to buy a new iPhone for the latest features that's their choice. I'm sure a lot of people will be happy to upgrade to the latest iPhone model if it offers faster speed or better battery life or camera flash.

  1. chas_m



    Multi-tasking is nice, but ...

    After 50M iPhones and 35M iPod Touches have been sold, apparently its not a deal-breaker.

    Yes, this DOES "inspire" me to consider an upgrade to my 2G original iPhone ... it's NOT a forced upgrade because this iPhone will continue to work exactly as it does now (unlocked/jailbroken by necessity). In fact, in some ways its a relief -- this iPhone won't run 4.0, which means I'll never have to go through the re-jailbreaking process again for this device.

    After 4.0 is out for a while (and in particular if an unlock solution emerges, since I have to have that for my situation), I'll look into upgrading. Till then, my original iPhone continues to give me great pleasure and does everything I ask of it, and I expect that to continue for at least a couple more years to come if necessary.

    Comment buried. Show
  1. wrenchy

    Joined: Dec 1969


    iPhone 4.0

    I smell..... An Android wanna-be.

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