Battery Life

Battery life is important beyond any doubt. No one wants a tablet or phone that can only spend three hours away from a charger before it dies, no matter how good the device is. While such battery life might be incredible for a desktop replacement or anything else that realistically spends most of its life plugged into a charger, mobile devices are usually carried on the go and used far away from a charger for significant amounts of time. Probably the ultimate example of this is travel, where one might use a tablet to watch movies and browse the internet for a few hours over the course of a flight.

As a result, a significant portion of our reviewing efforts are devoted to determining battery life. In order to quantify battery life, there are inevitably a lot of test cases to cover. Some people might spend most of their time in an e-reader app, others might spend most of their time playing games or similarly intensive tasks on their phones. There’s no real standard for usage, so a tablet that might last a day for one person could last a week. As a result, the goal of our testing is to provide a useful relative comparison. In order to do this, we attempt to equalize for variables like display brightness by setting all displays to 200 nits for battery life testing. Due to the inability to completely eliminate the variables that come with live network testing, we also use strong network reception with high throughput on LTE to ensure that things like power amplifiers are either at a low power setting or bypassed entirely.

Web Browsing Battery Life (WiFi)

Our first test is the venerable web browsing test, in which we load a selection of web pages from full charge until the device shuts off from lack of battery charge. In WiFi battery life is pretty much identical to the iPad Air 2, which might be surprising given that the battery is only 41% larger. That might sound like a lot, but the display of the iPad Pro is 77% larger at the same 264 PPI pixel density, which means that there’s a pretty sizeable efficiency gap between the iPad Air 2 and iPad Pro. The improved display and SoC are likely to be the main reasons for this, as the 20nm SoC process that was used to make the A8 SoC was quite leaky due to its traditional planar transistor structure compared to the FinFET process used in the A9X.

Web Browsing Battery Life (4G LTE)

Interestingly, for whatever reason when re-running the same test on LTE battery life is noticeably different when compared to the iPad Air 2, where LTE and WiFi battery life were relatively close. I suspect that RF power is pretty similar between the two devices, but due to efficiency improvements on the display/SoC side the difference in battery life due to additional RF power consumption is magnified.

Video Playback Battery Life (720p, 4Mbps HP H.264)

The more interesting test result that I encountered over the course of battery life testing was our tablet video rundown test. For whatever reason, web browsing clearly lasts a decent amount longer. It's pretty unlikely that the web browser has a lower SoC load when video is basically entirely dependent upon fixed function hardware decode. The most plausible explanation here for me is that we're seeing differences that arise from panel self-refresh, which can kick in on our web browsing test while the same definitely doesn't hold for our video test, which basically requires at least 30 FPS refresh rate continuously for the entire duration of the test. Overall that this makes the iPad Pro worse for content consumption, given Apple's content creation goals, is an unexpected turn of events.

BaseMark OS II Battery Life

Moving on to the more SoC-bound tasks, we can start by looking at Basemark OS II, which is basically a CPU power virus that can be used to examine the upper bound for device TDP, in addition to nominal sustained CPU load. It’s evident from this test and some back of the envelope calculation that total device TDP excluding display power is roughly 5W, which is about right given the size of the device. This suggests that the A9X can be directly compared to Intel’s Core M in both performance and power, for better or for worse. Performance here is good, with relatively low throttling due to the use of a FinFET process and solid implementation of the Twister architecture.

GFXBench 3.0 Performance Degradation

GFXBench 3.0 Battery Life

In our GPU throttling test, the A9X has effectively made it impossible to actually use T-Rex as a throttling test as it’s essentially pegged at vsync for the entire duration of the test. The iPad Pro also lasts a similar amount of time here as on the Basemark OS II test, which suggests that this test is still reaching TDP limits for the GPU, even if it doesn't manifest in the form of reduced performance.

Charge Time

While battery life is important, any time you’re dealing with a mobile device the time it takes to charge the battery is important as well. The usual example here is travel, but simply forgetting to plug in a device overnight can show the importance of charge rate. In the case of the iPad Pro, Apple ships it with their usual 12W charger. One might be tempted to suggest that the battery would be charged in about 3.5 hours, but it’s necessary to get the data and avoid speculation on something like this. In order to test how quickly the iPad Pro charges, we measure the difference in time between first plugging in a fully discharged tablet and when the charge is complete based upon power draw at the AC adapter.

Charge Time

Interestingly, the iPad Pro takes a pretty significant amount of time to charge, at over a full hour longer than the iPad Air 2. While some might be okay with this, it’s definitely a sore spot for the iPad Pro as a higher voltage charger would be able to charge the device at a more acceptable rate. I’m not really sure why Apple decided to go this route, but there’s really no clear solution here unlike the case of the iPhone 6s Plus. The charger also definitely isn’t enough to ensure that you’re always charging the iPad Pro while in use either if the SoC is in overdrive/turbo states as thermally constrained power draw is already around 9-10W.

Despite the long charge time, overall the iPad Pro is quite mobile. However, it does regress somewhat relative to the iPad Air 2 due to its longer charge time, even if battery life is equivalent. Depending upon your use case though it might be difficult, if not impossible to tell the difference.

System Performance Cont'd and NAND Performance Display
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  • ddriver - Friday, January 22, 2016 - link

    Should have named in iPad XL or something, this device will barely suit the need of any professional. Performance is good, but without supporting professional software, the hardware is useless.
  • Coztomba - Friday, January 22, 2016 - link

    And why would anyone bother to make professional software if the hardware wasn't capable? They needed a starting off point to say "Hey we can produce the hardware to run pro apps on a iPad. It's only going to get better. Start developing!"
  • ddriver - Friday, January 22, 2016 - link

    If anyone could stimulate software companies to do that, I guess that would be apple with its mountains of money and strong sales. They do have enough resources to do the software themselves.

    Mobile device hardware has been capable of professional workloads for at least 2-3 years. Nobody bothered to do it. Big software companies did not port their applications to ARM, instead they made cheap, crippled lesser versions. This is IMO a stupid move, they probably did this to promote their professional software to common folk, but it would have been more lucrative to bring professional software to mobile platforms.

    There are 2 main issues with mobile platforms - memory and CPU performance. Modern software is very bloated memory consumption wise, especially software relying on managed languages, the latter are also significantly slower in terms of performance than languages like C or C++.

    There is one big issue with legacy professional software - it originates back from the days developers were locked in platform specific application development APIs, so it represents a significant effort to port them to mobile platforms - essentially, most of the stuff needs to be rewritten.

    But a rewrite in faster and more efficient language, taking advantage of contemporary technology such as OpenCL can easily bring professional software to mobile platforms at an experience as good as that of desktop workstations. Naturally, more efficiently written software will also run that much better on powerful desktop machines as well.
  • mr_tawan - Friday, January 22, 2016 - link

    Not all pro are in the multimedia industry, you know :-).

    For most office workers, for instance, the only things they might need are notetaking (onenote), email (outlook), wordprocessor (word), and calendar (onenote). Most all tablet are capable to all of that, but it is a bit awkard to work with (due to the missing stylus, and not-so-comfy keyboard).

    With iPad Pro which, well, address this issue in the same way as the Surface Pro by adding keyboard and stylus to the tablet. It's much easier to use the table extensively (rather than just browsing web and watching video, which is hardly described as a profession job). So I personally think that adding these two options could takes the iPad into the 'professional' realm.

    I think that Apple would love to have iPad to complement MacBook (and Mac Pro), rather than to compete. If you need more power than just by Mac Pro :-).
  • ddriver - Friday, January 22, 2016 - link

    Yeah, why use one device when you can buy and lug around two devices instead.
  • melgross - Friday, January 22, 2016 - link

    There's actually quite a lot of professional software available on iOS, and has been for some time. I suppose if you do t use iOS, and so do t know what's a bailable, you can say that little is available, but it's simply not true. Microsoft itself had about two dozen professional apps on iOS. You really need to look through the App Store.
  • ddriver - Friday, January 22, 2016 - link

    What would those 24 ("two dozen") professional microsoft apps be?
  • Dave Bothell - Saturday, January 23, 2016 - link

    Word, Excel, PowerPoint, Outlook, OWA for iPad, Sunrise Calendar, OneDrive, OneDrive for Business, OneNote, SmartGlass, Skype, Bing for iPad, Remote Desktop, Lync, Office 365 Admin, Intune, Azure Authenticator, Sway, SharePoint Newsfeed, Dynamics CRM, Dynamics Business Analyzer, Dynamics Time Management, PowerApps, Global Startup Directory. There's more, but you asked for 24.
  • xerandin - Saturday, January 23, 2016 - link

    Smartglass isn't a professional app--it controls Xbox 360s or Xbox Ones, depending on which version of the app you install.
  • dsraa - Sunday, January 24, 2016 - link

    you forgot isnt a professional app either.

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