Limited RAM in Apple's A5 chip in iPad 2, iPhone 4S motivated by battery life concerns

Posted:
in iPad edited January 2014
Observers puzzled by the relatively scarce 512MB of RAM built into Apple's A5 processor used in this year's iPad 2 and iPhone 4S have received an explanation of sorts from an unlikely source: Microsoft.



Apple itself has never announced the amount of RAM built into the iPad or iPhone, forcing curious parties to poke its software and examine X-rays of its chips to arrive at the conclusion that the company's latest A5 chip has the same 512MB as the last generation A4 chip of the original iPad and last year's iPhone 4 (albeit RAM of the faster LPDDR2 type).



Competing smartphones and tablets commonly claim a full GB or more of RAM, which some pundits have identified as an area of superiority over Apple's offerings. In keeping with its tightly controlled, highly secretive design process, Apple has never acknowledged or commented on why the A5 (shown below) has so little RAM on board.







Given the direct historical relationship between available RAM and the sophistication of software a system can run, this has appeared to some as either an engineering failure by Apple, or alternatively an effort to boost margins at the cost of building a better product.



Answer from an unlikely source



However, a Microsoft blog post by Windows lead Steven Sinofsky highlights an interesting answer to a subject Apple itself has left unaddressed. In it, Sinofsky mentions "a key engineering tenet of Windows 8" that involved efforts "to significantly reduce the overall runtime memory requirements of the core system."



While the idea that the operating system should be as efficient as possible with available RAM is certainly not new, Sinofsky then introduced a detailed explanation authored by Bill Karagounis, the group program manager of Microsoft's Performance team, to detail exactly why using less RAM is so critically important.



Karagounis points out that "minimizing memory usage on low-power platforms can prolong battery life," noting that "In any PC, RAM is constantly consuming power. If an OS uses a lot of memory, it can force device manufacturers to include more physical RAM. The more RAM you have on board, the more power it uses, the less battery life you get.



"Having additional RAM on a tablet device can, in some instances, shave days off the amount of time the tablet can sit on your coffee table looking off but staying fresh and up to date," Karagounis wrote.



Windows 8 in 1 GB



In describing Microsoft's goals for getting Windows 8 to run on hardware with the same RAM as today's Windows 7, Karagounis compares the same system with just 1GB installed (the minimum required for Windows), and indicates that a base install of Windows 8 is now consuming just 281MB of available RAM, compared to 404MB for Windows 7.



Karagounis also notes that Windows 8 is actually doing more because it includes Microsoft's "Windows Defender" software intended to catch and block malware. He specifically notes that antivirus software requires a significant amount of RAM to address in working out how to prioritize memory allocation. That means Microsoft's malware issues raise challenges in RAM consumption unique to its platform.



Apple faces similar RAM constraints with its Mac OS X systems, which now also include basic malware software, although far less extensive and sophisticated than that required on Windows, where viruses not only exist in the wild but are very prevalent.



However, Microsoft's comments also pertain to Apple's iOS mobile environment, which is both scaled down and optimized to a much greater extent than even Mac OS X. While Apple's Macs now ship with a minimum of 2GB, Apple's iOS devices currently max out at just 512MB, and battery life is clearly a prime consideration.



Apple's iOS strategy also makes the concept of viruses essentially obsolete, not only because the devices can only obtain signed software from the App Store, but also because the operating system confines apps to their own sandbox. Even if an app were to pack a virulent payload, it simply couldn't deliver it in a way that infects other apps or documents because of iOS' security design. iCloud maintains a similar sandbox between the stored files of various apps.



The mythical half-tablet, half-PC



The comments of Microsoft's engineers also highlight the fallacy of thinking that Windows 8 will be able to usher in a new wave of tablets that can do double duty as light weight, long life iPad-replacements and then switch into high gear to work as full power Windows desktop machines at the owner's whim.



As Karagounis points out, having enough RAM to run a full Windows environment simply makes it impossible to match the efficiency profile of a system that is designed to use less RAM, because the installed RAM chips are going to be bleeding battery life regardless of whether they are being fully utilized or not. Simply having RAM installed means less battery life, a fact punctuated by the battery-sapping tablets running Android 3.0 Honeycomb on 1GB of RAM.



Microsoft's explanation effectively endorses Apple's strategy for designing hardware purpose-built for the task at hand, either with minimal RAM when designed to coast for days as a low power device like the iPad or iPhone, or with enough RAM to do full work, but requiring a recharge after several hours of operation, like Apple's MacBook line of notebooks.



This also further clarifies the idea that next year's ARM-based Windows 8 tablets will need to have minimal RAM to compete with the iPad, and therefore won't be able to run full scale desktop software, regardless of whether developers recompile it for ARM chips. Adding more RAM would not only take a hit on battery life but would also make the systems more expensive, and like Android 3.0 licensees, preclude them from matching Apple's iPad in price.



The Samsung-built, laptop-class tablet hardware Microsoft recently issued to demonstrate its newest build of Windows 8 for developers was initially chided for needing a fan to cool its Intel Core i5 processor, but the most telling detail of the system was that it packed 4GB of RAM, eight times as much as the iPad.
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Comments

  • Reply 1 of 70
    Okay, thanks Microsoft. Move along.
  • Reply 2 of 70
    moxommoxom Posts: 326member
    Interesting...
  • Reply 3 of 70
    stelligentstelligent Posts: 2,680member
    "key engineering tenant" ... Is Windows 8 a rental service?
  • Reply 4 of 70
    mstonemstone Posts: 11,510member
    iPhone sure, but the iPad has volumes of unused space that could accommodate a much larger battery to provide the needed power for the additional RAM. It might make it too heavy, but more RAM is better, in my opinion, as long as you can still deliver the long battery life that we currently enjoy on iPad.
  • Reply 5 of 70
    sflocalsflocal Posts: 5,958member
    "relatively scarce" RAM??? According to whom? Microsoft and the Android community whose half-baked OS's require higher horsepower hardware that suck more battery juice to perform the exact same processes that iOS can do effortlessly with less RAM?



    It looks like the PC/Android community is trying to keep an obsolete hardware business model going by using more and more power-hungry components to keep an industry afloat.



    Good for Apple that they can do more with less than the competition.
  • Reply 6 of 70
    docno42docno42 Posts: 3,709member
    Quote:
    Originally Posted by mstone View Post


    iPhone sure, but the iPad has volumes of unused space that could accommodate a much larger battery to provide the needed power for the additional RAM. It might make it too heavy, but more RAM is better, in my opinion, as long as you can still deliver the long battery life that we currently enjoy on iPad.



    Why is more RAM "better"?



    It's clearly not needed today and I don't want to lug around a bigger battery just so spec-oriented geeks can resolve their inadequacy issues



    A funny thing happens with resources - applications grown to consume them



    By forcing all iOS devices to have the same amount of RAM, programmers can't get lazy - "Well, I'll target it at the iPhone 4S and if it happens to work on the iPhone 4 or iPad 1, great"



    That just isn't an option.



    It's very similar to the video game consoles - the processing, GPU and memory in them is pitiful compared to full blown desktop PC's - yet stuff looks amazingly good on them. One aspect is the limited resources force developers to actually code efficiently. The other benefit is with consistent hardware developers can afford to get "down and dirty" with it and learn all the little tricks to extract the maximum performance. It's stable, so there is little concern that their effort will be wasted.



    iOS isn't as stable as consoles - there are a couple of new hardware platforms a year, but it's certainly less than the tens of thousands of new permutations of hardware and software for general purpose computers like PC's and Macs, and certainly less than the thousands of devices on Android.



    Apple's annual upgrade cycle represents a compromise of engineering, supply chain management and marketing and I think they have struck an excellent balance.



    Hardware platform stability is a perfect example of an intangible that looks trivial at first glance, but when you start digging deeper, reveals there is far more to it than just casually tossing updates on a whim...
  • Reply 7 of 70
    mstonemstone Posts: 11,510member
    Quote:
    Originally Posted by DocNo42 View Post


    Why is more RAM "better"?



    It's clearly not needed today and I don't want to lug around a bigger battery just so spec-oriented geeks can resolve their inadequacy issues



    A funny thing happens with resources - applications grown to consume them



    By forcing all iOS devices to have the same amount of RAM, programmers can't get lazy - "Well, I'll target it at the iPhone 4S and if it happens to work on the iPhone 4 or iPad 1, great"





    Some web pages could definitely use the additional ram. All that javascript makes the pages really big.
  • Reply 8 of 70
    801801 Posts: 271member
    Interesting, Thanks.
  • Reply 9 of 70
    apple ][apple ][ Posts: 9,233member
    This is basically the opposite strategy that Android phone and tablet manufacturers take. The final user experience and overall performance is not a primary concern.



    It's quite simple to build and manufacture a new Android phone.



    (1) Just use whatever new components that you can get your hands on so that you can play leapfrog with the last Android phone that just came out 2 weeks ago. In 2 weeks time, your new Android phone will be leapfrogged by another newly introduced Android phone, but who cares about that.



    (2) Whatever screen size they used in their previous phone, just make it at least an inch or two larger. Don't ever stop. Bigger is better. Just imagine that all of your customers are freaks of nature born with gorilla sized hands and that they're not really humans.



    (3) Putting in a lot of RAM in and the latest dual core CPU's are a must. This is of course done to mask the horrible performance of the Android OS, and even then it doesn't operate smoothly. It doesn't matter that your new Android phone is actually slower than other phones, you now have the higher specs to boast about on forums, even though your new phone actually operates slower and worse than other phones, not to mention the disgustingly horrible battery life that your phone will have.
  • Reply 10 of 70
    Quote:
    Originally Posted by mstone View Post


    iPhone sure, but the iPad has volumes of unused space that could accommodate a much larger battery to provide the needed power for the additional RAM. It might make it too heavy, but more RAM is better, in my opinion, as long as you can still deliver the long battery life that we currently enjoy on iPad.



    Did you read and understand the whole story? The conclusion is that you can't have the same battery life with more RAM. It is not possible with current technology.



    And it even stands to reason that future tech will consume less power if it is run with less RAM. Lean and mean is the best way. Nobody seems to understand this except Apple and believe it or not Microsoft. (Although Microsoft may have just copied the idea from Apple.)
  • Reply 11 of 70
    AppleInsider, Can we get the link to the Microsoft blog? It will help with fact checking. Thanks.
  • Reply 12 of 70
    You are aware that the A5 does not contain 512MB of RAM within the SoC... You seem to be implying this in your article and are incorrect.



    The 512MB of DDR SDram is off die, hence the DDR memory interfaces.
  • Reply 13 of 70
    The obvious reason for more RAM is so that the phone has to spend less energy getting costly resources over a 3G data connection again. It is important to note that all desktop operating systems are different from their mobile counterparts in that desktops can stick data in RAM onto the hard disk to be used later. Sure, there's a penalty when you have to grab that data from the hard disk again instead of RAM, but it's MUCH better than having to access network resources (and on a mobile device, using 3G is the largest penalty there is).



    As far as I know, none of the mobile operating systems have virtual memory because they don't want to wear out their Flash chips with continuous read/write cycles. Desktops and laptops don't really have this problem. Even Windows 8 tablets will write data to virtual memory.



    So I don't really buy the "less RAM = more power savings" argument on a mobile device. Any savings gained from having less RAM would quickly be wiped out by having to re-download images and other media assets from the web.
  • Reply 14 of 70
    stelligentstelligent Posts: 2,680member
    It's a valid point iP4 and 4S seem to work very well with 512MB of RAM.



    But it's also valid to point out that the Galaxy S2 has 1 GB of RAM and comparable battery life to iPhone 4 (longer talk time if you believe the specs, but who talks for 10-14 hours straight).



    Not saying the Galaxy is a better phone (not at all). But just saying that different engineering teams make different design compromises.
  • Reply 15 of 70
    Quote:
    Originally Posted by DocNo42 View Post


    Why is more RAM "better"?



    It's clearly not needed today and I don't want to lug around a bigger battery just so spec-oriented geeks can resolve their inadequacy issues



    A funny thing happens with resources - applications grown to consume them



    By forcing all iOS devices to have the same amount of RAM, programmers can't get lazy - "Well, I'll target it at the iPhone 4S and if it happens to work on the iPhone 4 or iPad 1, great"



    That just isn't an option.



    It's very similar to the video game consoles - the processing, GPU and memory in them is pitiful compared to full blown desktop PC's - yet stuff looks amazingly good on them. One aspect is the limited resources force developers to actually code efficiently. The other benefit is with consistent hardware developers can afford to get "down and dirty" with it and learn all the little tricks to extract the maximum performance. It's stable, so there is little concern that their effort will be wasted.



    iOS isn't as stable as consoles - there are a couple of new hardware platforms a year, but it's certainly less than the tens of thousands of new permutations of hardware and software for general purpose computers like PC's and Macs, and certainly less than the thousands of devices on Android.



    Apple's annual upgrade cycle represents a compromise of engineering, supply chain management and marketing and I think they have struck an excellent balance.



    Hardware platform stability is a perfect example of an intangible that looks trivial at first glance, but when you start digging deeper, reveals there is far more to it than just casually tossing updates on a whim...



    Let programmers be lazy. Targeting the smallest market isn't a good way to make money.
  • Reply 16 of 70
    Quote:
    Originally Posted by sflocal View Post


    "relatively scarce" RAM??? According to whom? Microsoft and the Android community whose half-baked OS's require higher horsepower hardware that suck more battery juice to perform the exact same processes that iOS can do effortlessly with less RAM?



    It looks like the PC/Android community is trying to keep an obsolete hardware business model going by using more and more power-hungry components to keep an industry afloat.



    Good for Apple that they can do more with less than the competition.



    Good God man, next time read the freaking article before you go off on a rant. MS was applauding Apple for their memory decisions, not bashing them.
  • Reply 17 of 70
    Quote:
    Originally Posted by dagamer34 View Post


    Let programmers be lazy. Targeting the smallest market isn't a good way to make money.



    No?! iOS developers make considerably more than strictly Android ones.
  • Reply 18 of 70
    banchobancho Posts: 1,517member
    Quote:
    Originally Posted by KaptainK View Post


    You are aware that the A5 does not contain 512MB of RAM within the SoC... You seem to be implying this in your article and are incorrect.



    The 512MB of DDR SDram is off die, hence the DDR memory interfaces.



    The RAM is contained inside the A5 package.
  • Reply 19 of 70
    wizard69wizard69 Posts: 13,377member
    Quote:
    Originally Posted by DocNo42 View Post


    Why is more RAM "better"?



    RAM is very important in iOS as you do not have demand paging of user data. This effectively puts constraints on what developer can do and often forces the developer to use different techniques. Techniques that may or may not impact performance.



    A classic Example is the viewing of PDF's which the 3G iPhone could not handle well at all. iPhone 4 does a much better job of handling large and complex PDFs. This is due directly to having more RAM in the device. Going to 512MB was a huge improvement in usability just considering the viewing of PDFs. The concept applies to all non trivial software though.

    Quote:

    It's clearly not needed today and I don't want to lug around a bigger battery just so spec-oriented geeks can resolve their inadequacy issues



    No you don't need it, that is not the same thing as saying that in general it isn't needed. It has nothing at all to do with spec-oriented geeks whomever they are, it is all about functionality and moving the platform forward. Admittedly this is a bigger deal on iPad than iPhone though. It really depends upon what you expect to get out of the platform.

    Quote:

    A funny thing happens with resources - applications grown to consume them



    The problem you run into is what happens if a new service significantly impacts the amount of RAM available to the device. It will be very interesting to see how much iS impacts RAM free to the app. One can argue if services like Siri are really needed but we still come back to platforms grow no matter what.

    Quote:

    By forcing all iOS devices to have the same amount of RAM, programmers can't get lazy - "Well, I'll target it at the iPhone 4S and if it happens to work on the iPhone 4 or iPad 1, great"



    That is an extremely negative way to look at the issue. A platform will become stagnate if it doesn't increase in capacity or capability over time. Look at what the first Mac Plus did and what you can do on a modern Mac Pro.

    Quote:

    That just isn't an option.



    What isn't an option?

    Quote:

    It's very similar to the video game consoles - the processing, GPU and memory in them is pitiful compared to full blown desktop PC's - yet stuff looks amazingly good on them. One aspect is the limited resources force developers to actually code efficiently. The other benefit is with consistent hardware developers can afford to get "down and dirty" with it and learn all the little tricks to extract the maximum performance. It's stable, so there is little concern that their effort will be wasted.



    How much game/app innovation is coming to consoles?

    Quote:

    iOS isn't as stable as consoles - there are a couple of new hardware platforms a year, but it's certainly less than the tens of thousands of new permutations of hardware and software for general purpose computers like PC's and Macs, and certainly less than the thousands of devices on Android.



    Apple's annual upgrade cycle represents a compromise of engineering, supply chain management and marketing and I think they have struck an excellent balance.



    In the iPhone it isn't a big deal. Part of that is due to systems like Android relying upon a Java like VM which itself can consume a great deal of RAM. In the end the apps aren't that bad off on iOS. At least when looking at cell phone platforms. However when discussing tablets it is a much bigger deal as more RAM can enable a far wider array of software and capabilities.

    Quote:

    Hardware platform stability is a perfect example of an intangible that looks trivial at first glance, but when you start digging deeper, reveals there is far more to it than just casually tossing updates on a whim...



    Meaningless comments. iPhone is no more a stable platform than any other. iPhone 4s for example has dual cores and a whole new GPU relative to previous iPhones. Stability is not about RAM. RAM is a straight jacket, sometimes such jackets are needed for the crazy but more often than not the are put not the dreamers and innovators.
  • Reply 20 of 70
    stelligentstelligent Posts: 2,680member
    Quote:
    Originally Posted by Bancho View Post


    The RAM is contained inside the A5 package.



    But the CPU and RAM are on different dies. So the other guy is right and you're not.
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