The Apple iPad Review (2012)
by Vivek Gowri & Anand Lal Shimpi on March 28, 2012 3:14 PM ESTThe 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.
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sjael - Wednesday, March 28, 2012 - link
On the 'A5X vs Tegra 3 In the Real World' page, you mention Modern Warfare 3 as a iOS+Android game.I think, since I haven't seen this game ported to phones/tablets, you *might* be thinking Modern Combat 3.
And then of course you show the market page for it further down..
Anand Lal Shimpi - Wednesday, March 28, 2012 - link
Correct - thanks for the heads up!Take care,
Anand
Celestion - Wednesday, March 28, 2012 - link
Looks like the 3rd gen iPad was CPU limited in that first GlBenchmark test.Anand Lal Shimpi - Wednesday, March 28, 2012 - link
That would be vsync :)Take care,
Anand
Celestion - Saturday, March 31, 2012 - link
I see. Thanks!Kevin G - Wednesday, March 28, 2012 - link
Memory bandwidth tests just seem to be off for what you'd expect a quad channel 128 bit wide memory bus to perform as. Performance didn't move from the dual channel 64 bit wide bus in the iPad 2. Could there be a software bug (Geekbench or iOS) limiting performance there? It'd be nice to revisit the memory tests after the next major revision of iOS and in conjunction with a later release of Geek Bench.Any chance of getting the exact resolution that Infinity Blade 2 runs on the rev 3 iPad? I'm assuming it'd be either 1536 x 1152 or 1368 x 1024 for quick scaling purposes.
slashbinslashbash - Wednesday, March 28, 2012 - link
They addressed this in the article."It would appear that only the GPU has access to all four channels." - Page 12
The GPU is hooked up to the RAM controllers. The CPU communicates to the RAM through the GPU. The GPU gets all 4 channels, the CPU only gets 2. The benchmark measures CPU-RAM bandwidth, not GPU-RAM bandwidth.
It's actually kind of interesting, as it's an inversion of the typical architecture that we're all used to from PCs. But it makes sense, since the new iPad is basically a very nice screen with a smartphone CPU attached. The very nice screen requires a very nice GPU to drive it, so the GPU is more important (and would be memory starved with only 64 bits). The CPU just has to be "good enough" while any shortcomings in the GPU would be magnified at this resolution.
tipoo - Wednesday, March 28, 2012 - link
Which way is the PS Vita configured? That has the same quad core GPU and a quad core CPU as well.tipoo - Wednesday, March 28, 2012 - link
Huh, the Vita actually has 128mb dedicated video memory, can't find the bandwidth though.pickica - Monday, April 2, 2012 - link
We should also consider a possible higher clock on Vita.