The Impact of Larger Memory

Apple doubled memory capacity on the new iPad to 1GB, marking the first time in recent history that Apple's flagship product offers a similar amount of memory to the current crop of high-end Android devices. Apple's iOS can do a relatively good job with limited system memory as it will conservatively unload applications from memory in the event that it needs to free up more space. iOS does not support paging to flash, making DRAM size a hard limit for developers looking to really push the platform.

Apple has always been conservative on DRAM sizing because it's a great way of reducing the BOM (Bill of Materials) cost. If Apple can make up for having less DRAM by being more aggressive in software (read: kicking apps out of memory), it's a tradeoff that makes sense. It's really Apple's foray into gaming that has added pressure to increase memory sizes.

With the move to the Retina Display, the amount of memory needed to store a single frame increases by 4x—from 3MB to 12MB. Assuming two buffered frames you're looking at 24MB of RAM just to smoothly display what you're seeing on the screen.

The bigger problem isn't the frame buffer, but rather all of the other data you need (e.g. level data, textures, etc...). The higher the screen resolution, the more important it is to have higher quality assets in your game. Texture compression can go a long way, but at some point there's simply more data to deal with as game complexity increases. It's not just about the increase in resolution either. As GPU horsepower increases, so will the complexity of what game developers try to build.

While the frame buffer size increased thanks to the Retina Display, total system memory increased by a much larger amount. With 1GB of memory, game developers are now less constrained.

A more immediate benefit is apps and web pages will remain resident in memory longer as you open open up and switch to other apps. For example, on the iPad 2 if I open four tabs in Safari (AT, Engadget, Reddit, and Tech Report), open iPhoto, run Infinity Blade 2 and GTA 3, switching between the latter two will always require a full game reload (as in you see the intro and everything before you pick up where you left off). On the new iPad, with the same setup, I can switch between Infinity Blade 2 and GTA 3 and automatically resume where I last left off thanks to the extra DRAM. You can still create a scenario where even 1GB isn't enough, it's just that the limit is now higher than it was on the iPad 2.

A Word on Packaging & Looking Forward GPU Performance
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  • PeteH - Wednesday, March 28, 2012 - link

    No idea. Was it necessary to upgrade the GPU to get an equivalent experience on the larger screen in that case, or was performance on the 3GS limited by the CPU (or RAM, or something else)? Reply
  • zorxd - Thursday, March 29, 2012 - link

    just look at benchmarks on this web site

    The iPhone 3GS gets more FPS in 3D games because of the lower resolution.

    So in short, yes, it would have been necessary to upgrade the GPU to keep the same performance.

    But no matter what Apple does, people will always say it's the right choice.
    Reply
  • PeteH - Thursday, March 29, 2012 - link

    I looked for a comparison between 3GS and 4 game FPS comparison and couldn't find anything. Can you point me to it?

    I'm looking for hard numbers because just increasing the resolution doesn't necessarily mean a GPU upgrade is necessary. If (and this is completely hypothetical) the 3GS was performance limited because of its CPU, improving the CPU in the 4 could allow it to achieve the same performance at a higher resolution.

    I'm not remotely saying this is the case, just that I've seen no numbers demonstrating a drop in frame rate from the 3GS to the 4.
    Reply
  • dagamer34 - Friday, March 30, 2012 - link

    I believe the GPU got a clock speed increase when it went from the 3GS to the 4. Reply
  • Peter_St - Monday, April 2, 2012 - link

    Oh wait, let me rephrase this: I have this nice shiny tower with 2GB of RAM and newest CPU out there but shitty OS with java hogs and memory leaks, but who cares, I'll just go and jerk off on the specs.

    I think that's what you wanted to say...
    Reply
  • tipoo - Wednesday, March 28, 2012 - link

    GPUs which consume hundreds of times more watts than SoCs like this and have much more memory bandwidth at their disposal still struggle with the resolution this thing is displaying. The Xbox 360 GPU has, if I recall, around 25GB/s vs 6 in this, and that struggles to run games at 720p in a constant 30FPS. So far, it seems like the retina compatible games do display at native res, but there aren't any improvements in textures, effects, etc. So would the additional GPU power effectively be negated by the resolution for native apps, and still be constrained to games that look straight out of 2003-4? Or is Imagination Tech's video memory compression that much more advanced than AMDs/Nvidias so bandwidth doesn't matter as much? Reply
  • zorxd - Wednesday, March 28, 2012 - link

    It's not only about the resolution. You could probably play Doom just fine with the SGX543MP4 at this resolution. The problem is when you have more complex level of details, shaders, etc. The iPad couldn't play a game like Crysis even at half resolution. But even at 2048x1536, Doom will still look like a game of the 90s. Reply
  • tipoo - Wednesday, March 28, 2012 - link

    *12.8GB/s, my mistake Reply
  • BSMonitor - Wednesday, March 28, 2012 - link

    What's battery life watching a bunch of movies.. say from New York to Hawaii? Will I be able to get 9 hours??

    Can run all the compute benchies we want, but primarily these are portable entertainment devices. The simplest use being the most common.
    Reply
  • PeteH - Wednesday, March 28, 2012 - link

    Depends how bright you want the display, but from the number they're posting you should be fine at < 70% max brightness.

    I would argue that the most common use case is probably web browsing though, not movie watching. Unless... how often are you on these flights from New York to Hawaii?
    Reply

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