Usability & iOS 7

The iPad Air remains one of the best consumer tablet experiences around. The OS and Apple’s first party applications are both extremely well suited to the tablet, and there’s a very healthy ecosystem of third party applications to fill in the gaps left by Apple.

Lately Apple has been doing wonders to limit those gaps. Both iLife and iWork suites are now free with the purchase of any new iOS 7 device, including the iPad Air. Previously each of the three iLife apps set you back $5 a piece ($15 total), while the iWork apps were priced at $10 a piece ($30 total). Apple has truly embraced its role as a devices and software company and is using the latter to help sell the former. On the one hand this is an admission that the market is growing more competitive, as tossing in free software is a great differentiator. On the other hand, freeing up iLife/iWork is a vote of confidence in Apple’s ability to continue to demand a premium for its hardware. Neither suite comes preinstalled on the iPad Air, but upon a visit to the App Store users are reminded that they can get all six of the apps for free if they should desire to. I suspect part of the reason that they’re not bundled by default is to avoid eating up space on the devices with less NAND by default.

The core iOS apps are quite approachable and easy to use. Applications like Safari and Mail make great use of the high resolution screen. Obviously the same can be said for things like Photos and iPhoto. The virtual keyboard experience is great on the large display (especially in landscape mode). Honestly, if there was a good Google Hangouts app (the Android version is much better in my experience) for iOS 7 I think I could be very comfortable and productive on the iPad Air.

I find that task switching is far better on the iPad than it is on the iPhone since multitasking gestures are supported. A four finger swipe left/right between applications or up/down to bring up the task switcher is so much quicker for me than a double tap of the physical home button. Similarly a five finger pinch to get back to the home screen from any application is significantly faster. The new iOS 7 multitasking UI feels so much more at home on the iPad’s large display as well.

My only complaint about task switching on the iPad Air is that UI frame rate will regularly drop below 30 fps during some of these transitions. The added GPU performance on the A7 doesn't seem to really impact things compared to the A6X, so I’m fairly convinced at this point that the solution to the problem will have to come in software. It’s quite reminiscent of the Retina MacBook Pro UI frame rate issues under Mountain Lion, although not nearly as bad (and I’m hoping it won’t take a year to get these ones resolved).

The release of iOS 7.0.3 addressed (at least partially) some of my concerns around the OS. As I already mentioned, stability on 64-bit platforms seems somewhat improved - at least compared to the initial release of iOS 7. The other big improvement in my mind is the ability to turn off/reduce the transition animations. The impact to usability on the iPhone 5s is huge, but it’s also pretty significant on the iPad Air. The animations themselves are pretty but I find that they get repetitive after continued use.

Memory Size & The Impact of 64-bit Applications

The iPad Air, like the iPhone 5s, ships with 1GB of LPDDR3 memory. Apple frowns upon dissection of review samples but I think it’s a safe bet that we’re not talking about a PoP (Package-on-Package) configuration but rather discrete, external DRAM here. It’s also probably a safe bet that even the iPad mini with Retina Display will ship with 1GB of memory as well.

Something I didn’t have time to address in my iPhone 5s review was the impact of 64-bit applications on memory usage. I actually ran some tests after the 5s review hit but never got the chance to share the data, so I figured now is as good a time as any to do just that.

Unlike traditional desktop OSes, iOS doesn’t support paging to disk (or in this case, NAND). Application data can either reside in memory or the associated process is terminated and has to be reloaded the next time you request it. It’s a decision likely made to both maintain user experience and limit the number of program/erase cycles on the internal NAND.

The good news is that iOS was architected to run on as little hardware as possible and as a result tends to be quite memory efficient. There are also power implications of going to larger memories. The combination of these two things has kept Apple on the conservative side of increasing memory capacity on many iDevices.

The move to a 64-bit platform however does complicate things a bit. Moving to a larger memory address space increases the size of pointers, which in turn can increase the footprint of 64-bit applications compared to their 32-bit counterparts. So although there’s clearly a performance uplift from app developers recompiling in 64-bit mode (more registers, access to new instructions), there’s also an associated memory footprint penalty. Since the iPad Air and iPhone 5s don’t feature a corresponding increase in memory capacity, I wondered if this might be a problem going forward.

To find out I monitored total platform memory usage in a couple of scenarios. Before measuring I always manually quit all open apps and performed a hard reset on the device. Note that the data below is reporting both clean and dirty memory, so it’s possible that some of the memory space could be recovered in the event that another process needed it. I hoped to minimize the impact by always working on a cleanly reset platform and only testing one app at a time.

I looked at memory usage under the following scenarios:

1) A clean boot with no additional apps open
2) Running Mobile Safari with 4 tabs open (two tabs, two tabs, all showing the same content)
3) Infinity Blade 3 (64-bit enabled) sitting at the very first scene once you start the game
4) iOS Maps in hybrid view with 3D mode enabled, with a WiFi assisted GPS lock on my physical location
5) Google Maps in the same view, under the same conditions. I threw in this one to have a 32-bit app reference point.

In general you’re looking at a 20 - 30% increase in memory footprint when dealing with an all 64-bit environment. At worst, the device’s total memory usage never exceeded 60% of what ships with the platform but these are admittedly fairly light use cases. With more apps open, including some doing work in the background, I do see relatively aggressive eviction of apps from memory. The most visible case is when Safari tabs have to be reloaded upon switching to them. Applications being evicted from memory don’t tend to be a huge problem since the A7 can reload them quickly.

The tricky part is you don’t really need all that much more memory. Unfortunately as with any dual-channel memory architecture, you’re fairly limited in how you can increase memory capacity and still get peak performance. Apple’s only move here would be to go to 2GB, which understandably comes with both power and financial costs. The former is a bigger concern for the iPhone 5s, but on the iPad Air I would’ve expected a transition sooner rather than later.

Although things seem to have improved with iOS 7.0.3, the 64-bit builds of the OS still seem to run into stability issues more frequently than their 32-bit counterparts. I still see low memory errors associated with any crashes. It could just be that the move to 64-bit applications (and associated memory pressure) is putting more stress on iOS’ memory management routines, which in turn exposes some weaknesses. The iPad Air crashed a couple of times on me (3 times total during the past week), but no where near as much as earlier devices running iOS 7.0.1.

Battery Life Final Words


View All Comments

  • stingerman - Sunday, November 3, 2013 - link

    Yes, I haven't even seen one of those in use other than commercials. Real failures... Reply
  • stingerman - Sunday, November 3, 2013 - link

    lol, you're hilarious! iOS is Unix plus all the major OS X frameworks plus all the new iOS frameworks... It maybe light because of its elegance, but it's a light nuclear weapon... Reply
  • lilo777 - Sunday, November 3, 2013 - link

    LOL. Do you know any version of Unix that does not have a file system (exposed to user)? Reply
  • Krysto - Friday, November 1, 2013 - link

    Offtopic, but Anand, the announcement of Mali T760 is suspiciously missing from this site.

    Over 300 GFLOPS, which is more than PS3 and should make it pretty competitive with mobile Kepler, along with ASTC compression by default, much more efficient, and has some interesting features like hardware assisted global illumination.

    ARM's announcement:
  • michael2k - Friday, November 1, 2013 - link

    Yeah, the T700 series is for next generation devices, or in other words, products in the next 12 months. The PowerVR6 series is available now for this generation and up to 1000 GFLOPS. Reply
  • Krysto - Saturday, November 2, 2013 - link

    Do you see that 1000 GBFLOPS in any smartphone? Just because it can be scaled that much, doesn't mean they WILL for smartphones. This GPU will be used in smartphones a year from now. What does the GPU in Apple's A7 have now? ~100 GFLOPS?

    Anyway, the Mali T760 seems very competitive with what will be out there a year from now, and Anandtech usually writes about these sort of announcements.
  • michael2k - Monday, November 4, 2013 - link

    I think you've missed the point.
    1) We aren't in a smartphone thread
    2) The PowerVR6 will scale to 1000 GFLOPs; so when the T700 comes out next year, the PowerVR will be ready
    3) The Air is at about 115 GFLOPs, about 2x the outgoing iPad 4, and will therefore be approximately 230 GFLOPs in the A8 next year, if 2x, or 340 GFLOPs if 3x

    So you are correct that the Mali T760 will be competitive next year, but this article is about this year.
  • michael2k - Monday, November 4, 2013 - link

    You've missed the point.

    The PVR6 is 115GF today in the Air, and when needed to compete with the T700 can hit 300GF.

    Likewise, we are in a thread about tablets, where it is much more likely to scale to the needed 300GF.
  • Krysto - Saturday, November 2, 2013 - link

    What you said also reminded me of how Intel promoted "Haswell graphics".

    "Hey, look, out "Haswell GPU" (Iris Pro 5200) is 3x faster than IVB!" - and then you only see crappy 4600 in most devices, including the Surface Pro, which is only 20 percent faster than last year's IVB GPU.

    Or "look at our awesome new 2.6 Ghz Silvermont CPU's! - and then you only see 1.3 ghz Silvemont for tablets, because the 2.6 Ghz ones are not viable either because of too high TDP or price, which makes them pretty irrelevant. What's relevant is what will be in the market, not their pie-in-the-sky CPU's that never get on the shelves.
  • ashleyuv - Saturday, November 2, 2013 - link

    This is a very interesting review, even for someone without the tech or IT background to follow all of it. In particular, I like the way, in the last part, you show how the increase to 64-bit and the DRAM size (remaining the same), while seeming like a no-brainer and conservative decisions, respectively, are actually a smart play, albeit one with consequences.

    In agreement with one of your readers, I'd have to say that "review" is really the wrong word for this. It is all but a scientific study. But again, it's written for people who may not have an extensive tech background.

    Thank you! I will be reading more in the future (just discovered your site).

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