The Apple iPad 2 Review
by Brian Klug, Anand Lal Shimpi & Vivek Gowri on March 19, 2011 8:01 PM ESTBattery Life
Testing battery life on a tablet is pretty grueling as these things are effectively smartphones with gigantic batteries. What would last for only a few hours on a smartphone can easily last over ten on a tablet. The iPad 2 is no exception.
As iFixit discovered, the iPad 2 features a nearly identical battery to the original iPad (25Wh vs. 24.8Wh). We already established that display brightness hasn't gone up so the only real impact on battery life will be because of the A5 SoC.
The iPad 2 WiFi's battery, courtesy iFixit
The ARM Cortex A9 tends to be more power efficient than its predecessor, the A8. With a shallower pipeline and the ability to execute instructions out of program order you get better performance per watt in most cases. As a result the A5 should complete bursts of instructions quicker than the A4 and get back to sleep sooner.
To put this to the test we put together a battery life test that combined our non-Flash smartphone web browsing test, checking for email every 15 minutes (via a Gmail account receiving ~100 emails per day) and constant local music playback while all of this is going on. The results are pretty much as expected:
Over WiFi the Motorola Xoom and iPad 1 deliver very similar results. The iPad 2 pulls ahead by around 8%, it's not a huge advantage but it's there. Over 3G there's a noticeable drop in battery life, putting both of the iPad 2s below 10 hours and kicking the Xoom down to under 9 hours. All of the numbers on this chart are respectable however and you can expect a good day's worth of use out of any of these tablets.
Note that while the iPad 2 did better than its predecessor if you were to run an app that pegged both CPU cores at 100% you'd see reduced battery life on the iPad 2 vs. the iPad 1. Granted you'd also see better performance on the iPad 2.
Video playback is obviously an important function of these new tablets so we put together a H.264 decode playback test as well. For this test we transcoded a copy of Quantum of Solace from a 1080p BD source down to a 720p H.264 using Handbrake's Normal encode profile with one modification. In order to enable smooth playback on the Motorola Xoom we had to disable b-frames in the encode. The results are below:
The iPad 2 consistently lasted longer than the original iPad in our video playback test. The Xoom however did noticeably worse. Unfortunately only a portion of the H.264 decode pipeline is accelerated by NVIDIA's Tegra 2 in this test. When playing back anything more strenuous, portions of the pipeline are handled by the CPU cores in software. If you were to enable b-frames the Xoom would not only stutter but its battery life would drop to around 6 hours.
On the iPad 2 its Cortex A9s are mostly powered down during this test, on the Xoom the A9s are helping with the heavy lifting for video decode and as a result we see lower battery life. Kal-El is expected to address this issue head on.
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Mike1111 - Sunday, March 20, 2011 - link
Well, Anandtech is a site for geeks, but shouldn't you have at least mentioned how you think the iPad 2 could fit into the average person's life? People who don't "work" with PCs in their free time and who don't have a dedicated PC workflow?Some thoughts regarding the review:
- I thought the glass was supposed to be from Asahi Glass (Dragontrail)?
- Okay, the Xoom can't play videos with b-frames without problems. But what h.264 videos can the iPad 2 play? Same as iPad? More? High-profile? Blu-ray class h.264 videos?
- I wish you could have gone more in-depth regarding the A5. Why is it so big compared to the Tegra2? How efficient does it work? What kind of video decoder/encoder are used? etc.
Zebo - Sunday, March 20, 2011 - link
Nothin like the real things baby.....I have used a x201 tablet since April of 10 and it's the best investment I ever made. True outdoor viewable with upgraded outdoor IPS screen and 500 nits. true keyboard, true duel core processor, true work machine. I have ATT card to get internet and take it everywhere I go. I bet I travel more than Anand and it's the only way to fly.tcool93 - Sunday, March 20, 2011 - link
I don't even own the Ipad. Yet I do know for a fact there are at least two other browsers you can use with it besides Safari. The Atomic browser, and the Skyfire browser... both supporting tabs and supposedly are much better than Safari. Skyfire even has partial flash support, and viewing social network sites built in (twitter, facebook, etc). Both of those browsers have very good reviews also.secretmanofagent - Sunday, March 20, 2011 - link
I'm starting to play with iCab, but I don't have an iPad.dagamer34 - Sunday, March 20, 2011 - link
3rd party browsers unfortunately don't get the Javascript speedup built into iOS 4.3tipoo - Sunday, March 20, 2011 - link
The javascript engine is built into the browser. Of course they don't get the faster Safari engine, they aren't Safari. They use their own engines.name99 - Sunday, March 20, 2011 - link
Yes and no.The current iOS will no allow third party apps to create code on the fly, so those browsers will not be able to use JIT'ing, even if they wanted to write a sophisticated javascript engine.
On the other hand, Apple is well aware of the limitations of their current browser tech and are actively working on ways to run different parts of the browsing code in different processes (for both performance --- multi-threading, non-blocked UI --- and security reasons), on both OSX and iOS.
When this effort comes to fruition, who knows how much of the underlying tech (in particular, in this case the ability to create code on the fly, perhaps in some sandboxed fashion) will be made available to devs?
Zebo - Sunday, March 20, 2011 - link
You'll never even think about a slate tablet after that.10 hrs battery
all windows apps
plays games
IPS screen (with upgrade)
can use as HTPC when on road
can publish this site effortlessly
I doubt you'll use a another device besides your iphone
VivekGowri - Sunday, March 20, 2011 - link
And I could buy three iPads for the same price. It simply isn't a valid comparison for the same reason the MB Air, Asus Slate, and other $1000+ devices aren't; not in the same category, not even in the same price range. It's like saying that after driving a Mercedes S-class, you'll never think about driving a Lotus Elise or Porsche Boxster ever again - it's not really a useful or valid comparison to make.I don't doubt that the X220t is going to be an excellent, excellent device - fixes every problem I had with the X200/201t, goes back to the IPS display, and it's going to be pretty fast too. It looks pretty awesome, IMO. If I was in the market for a tablet PC (as opposed to a smartphone-based tablet), this and the ASUS Slate would be the only two I'd really look at - the ASUS is kind of like a cheaper version of the X220 except without the built-in keyboard.
snouter - Sunday, March 20, 2011 - link
But I left it on a plane. What did I replace it with? An 11" MacBook Air. Honestly, it's no comparison. The Air can do so many things that the iPad could not. Tablets will stick around and find niche applications in lots of places, but I'd keep my eye on the the super thin super light notebooks. BTW, the Air has a ULV Core 2 Duo 1.6GHz and will get Sandy Bridge in the next update. The processing power is far superior to the tablets and the netbooks. It's everything I wanted to do with my iPad, and it's a notebook when I need it to be. Main main work Laptop is still a 17" MacBook Pro, but none of these tablets, netbooks or ULV laptops are in competition with it. When the next Air comes out with a backlit keyboard and ULV Sandy Bridge, I'll be there.