The Apple iPad Review (2012)
by Vivek Gowri & Anand Lal Shimpi on March 28, 2012 3:14 PM ESTBattery Life
For a company that has been so laser focused on reducing weight and device thickness, the new iPad actually growing in both of these dimensions was unexpected. From a technical standpoint, the tradeoff makes sense. The new Retina Display consumes significantly more power than its predecessor, as do the A5X and MDM9600 baseband. Both of those ASICs are still built on a 4x-nm LP process and will surely increase power consumption over the iPad 2.
With more transistors switching on the same process node and a display (and backlight) driving more pixels at the same brightness, the battery either had to be larger or battery life would suffer. Apple understandably chose the former and the new iPad ships with a 42.5Wh battery—the largest we've ever seen used in an ARM tablet. The new iPad's battery is so large it's even bigger than what Apple uses in the 11-inch MacBook Air, and it's within striking distance of the 50Wh unit you'll find in the 13-inch model. I do believe this move says a lot about how Apple sees the iPad moving up in the world, but I'll get to a discussion about that later.
With a 70% larger battery than the iPad 2 but with more power hungry components inside, how does the new iPad fare in real world usage? Subjectively: it doesn't last as long as its predecessor. Objectively, our numbers seem to agree.
Our web browsing battery life test browses through dozens of web pages, pausing on each to simulate reading time, until the battery is depleted. All of our tests are run at the same brightness settings (200 nits) to ensure we are comparing apples to apples.
On WiFi we measured an 8% decrease in battery life compared to the iPad 2—nothing huge but not insignificant either. Fall off of WiFi and depend on LTE and you'll see around a 9% decrease in battery life, again—noticeable but not unusable.
I also threw in numbers from the Motorola Xyboard 10.1, an LTE enabled Android tablet running 3.2. Equipped with a much smaller battery (~26Wh), the Xyboard 10.1 delivered 7.31 hours in our LTE web browsing test. The new iPad managed to last 16% longer on a single charge—a smaller advantage than you'd expect given the 70% increase in battery capacity, showing just how much power the new Retina Display and its backlight consume.
The iPad is more than usable on long flights or throughout the day without being tethered to a wall outlet, but in practice you can expect a decrease in battery life compared to last year's model.
Keep in mind that these values are all at 200 nits (roughly 70% brightness on the iPad). If you use the iPad at max brightness (~400 nits) you'll see considerably lower numbers:
In our web browsing test, at max brightness, we saw 5 hours and 34 minutes of continuous use before the battery died. The iPad 2 incurs a similar penalty, lasting under 7 hours in the same test. Do keep this in mind if you need to get a lot of untethered use out of the new iPad. In order to come close to Apple's battery life estimates you'll have to be below 70% brightness.
Charging
Despite the significant increase in battery capacity, Apple continues to ship the new iPad with the same 10W USB power adapter as the previous two models. You can charge the iPad via a Mac/PC USB port that implements the USB charging spec, however doing so will take a minor eternity to fully charge the tablet. Just as before, the new iPad will not charge off of a USB port if the tablet is awake; it will only charge when locked/asleep. The convenience of having a USB based charger is evident, but you'll want to stick with the 10W adapter to actually charge the iPad.
Charging the larger battery does take longer. If we measure from a completely dead state to when the iPad indicates that it's fully charged the increase in time is approximately 50%, from 4 hours with the iPad 2 to 6 hours with the new iPad. ASUS' Transformer Prime, by comparison, requires only 2.5 hours as it ships with an 18W charger. And no, you can't use ASUS' charger to speed up charge times on the new iPad—when connected, the TF Prime charger will only supply 9W to the iPad.
The story doesn't end there however. While the iPad 2 will draw 0W after its 4 hour charge cycle is complete, the new iPad will continue to draw around 3W after it claims to be fully charged. This will continue for roughly another hour at which point the power adapter will draw anywhere from 0.1—0.6W.
Note that when running at full brightness and with a heavy GPU load (e.g. Infinity Blade 2), the power adapter can't supply enough to keep the iPad charged and drive the display/internal components.
There's no good solution here other than for Apple to start shipping the iPad with a higher wattage power adapter. I do believe faster charge times are going to be necessary if Apple is keen on sticking with this larger battery, not to mention the usage issues of not being able to maintain charge equilibrium under load.
Thermals
The increase in power consumption of the new iPad also manifests in the form of increased heat production. A 163mm^2 SoC built on a 45nm LP process is a serious chip. Although it doesn't run hot enough to require active cooling, the SoC alone is responsible for a couple of watts of the iPad's TDP under heavy load. Combine that with a 45nm LTE modem and the heat put off by the more powerful backlight and you've got a recipe for a noticeably warmer device.
Does the new iPad get warmer than the previous one? Absolutely. I would even go as far as to say that it can get uncomfortably warm, but it never gets too hot to hold. If you've used any of the modern Mac notebooks, I don't believe it's anywhere near as bad.
When holding the new iPad in portrait mode, with the home button at the bottom, the lower left corner of the device ends up being the warmest. Along the left edge of the iPad is where the logic board resides, and the lower half is home to the A5X SoC. Under load, particularly a heavy GPU load (e.g. playing a 3D game), this area is going to heat up quickly.
I took several measurements using a contactless IR thermometer in the same ambient conditions on a new iPad vs. the iPad 2. The results are below:
| Thermal Comparison (Max Temperature) | |||||
| iPad 2 | iPad (3rd generation) | ||||
| Web Browsing (2 hours) | 32.7˚C | 37.6˚C | |||
| Infinity Blade 2 (1 hour) | 34.2˚C | 41.9˚C | |||
Again, I don't believe this is a deal breaker but it's the obvious result of remaining on Samsung's 45nm LP process combined with a more power hungry display/backlight. I suspect there will be improvements in efficiency on the display side over time, but I can't see the Retina Display being any lower power than the iPad 2's 1024 x 768 screen. The real avenue for improvement will be when Apple shifts to 28/32nm silicon for the SoC and LTE modem. If you want a cooler running iPad, you'll have to wait until next year for that.
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name99 - Friday, March 30, 2012 - link
Just to clarify, this is NOT some Apple proprietary thing. The Apple ports are following the USB charging spec. This is an optional part of the spec, but any other manufacturer is also welcome to follow it --- if they care about the user experience.darkcrayon - Thursday, March 29, 2012 - link
All recent Macs (last 2-3 years) can supply additional power via their USB ports which is enough to charge an iPad that's turned on (though probably not if it's working very hard doing something). Most non-Mac computer USB ports can only deliver the standard amount of USB power, which is why you're seeing this.Your Lenovo *should* still recharge the iPad if the iPad is locked and sleeping, though it will do so very slowly.
dagamer34 - Friday, March 30, 2012 - link
I did the calculations and it would take about 21 hours to recharge an iPad 3 on a normal non-fast charging USB port from dead to 100%. Keep in mind, we're talking about a battery that's larger in capacity than the 11" MacBook Air.snoozemode - Thursday, March 29, 2012 - link
http://www.qualcomm.com/media/documents/files/snap...Aenean144 - Thursday, March 29, 2012 - link
Anandtech: "iPhoto is a very tangible example of where Apple could have benefitted from having four CPU cores on A5X"Is iPhoto really a kind of app that can actually take advantage of 2 cores? If there are batch image processing type functionality, certainly, though I don't know if iPhoto for iOS has this type of functionality. The slowness could just be from a 1.0 product and further tuning and refinement will fix it.
I'm typically highly skeptical of the generic "if the app is multithreaded, it can make use of all of the cores" line of thought. Basically all of the threads, save one, are typically just waiting on user input.
Anand Lal Shimpi - Thursday, March 29, 2012 - link
It very well could be that iOS iPhoto isn't well written, but in using the editing tools I can typically use 60 - 95% of the A5X's two hardware threads. Two more cores, at the bare minimum, would improve UI responsiveness as it gives the scheduler another, lightly scheduled core to target.Alternatively, a 50% increase in operating frequency and an improvement in IPC could result in the same net benefit.
Take care,
Anand
shompa - Friday, March 30, 2012 - link
*hint* Use top on a iOS/Android device and you will see 30-60 processes at all time. The single threaded, single program thinking is Windows specific and have been solved on Unix since late 1960. Todays Windows phones are all single threaded because windows kernel is not good at Multit hreding.With many processes running, it will always be beneficial to have additional cores. Apple have also solved it in OSX by adding Grand central dispatch in their development tools making multithreaded programs easy.
Iphoto for Ipad: Editing 3 million pixel will demand huge amount of CPU/GPU time + memory. Apple have so far been able to program elegant solutions around the limits of ARM CPUs by using NOVA SIMD extensions and GPU acceleration. An educated guess is that Iphoto is not fully optimized and will be at later time.
(the integrated approach gives Apple a huge advantage over Android since Apple can accelerate stuff with SIMDs. Google does not control the hardware and can therefore not optimize its code. That is one of the reasons why single core A4 was almost as fast as dual core Tegras. I was surpassed when Google managed to implement their own acceleration in Andriod 4.X. Instead of SIMD, Google uses GL, since all devices have graphics cards. This is the best feuture in Android 4.x.)
name99 - Thursday, March 29, 2012 - link
[/quote]Apple’s design lifespan directly correlates to the maturity of the product line as well as the competitiveness of the market the product is in.
[/quote]
I think this is completely the wrong way to look at it. Look across the entire Apple product line.
I'd say a better analysis of chassis is that when a product first comes out, Apple can't be sure how it will be used and perceived, so there is some experimentation with different designs. But as time goes by, the design becomes more and more perfected (yes yes, if you hate Apple we know your feelings about the use of this word) and so there's no need to change until something substantial drives a large change.
Look, for example, at the evolution of iMac from the Luxo Jr version to the white all-in-on-flatscreen, to the current aluminum-edged flatscreen which is largely unchanged for what, five or six years now. Likewise for the MacBook Pro.
Look at the MacBook Air. The first two revs showed the same experimentation, trying different curves and angles, but Apple (and I'd say customers) seems to feel that the current wedge shape is optimal --- a definite improvement on the previous MBA models, and without anything that obviously needs to be improved. (Perhaps the sharp edges could be rounded a little, and if someone could work out the mechanicals, perhaps the screen could tilt further back.)
And people accept and are comfortable with this --- in spite of "people buy Apple as a fashion statement idiocy". No-one will be at all upset if the Ivy League iMacs and MBAs and Mac Minis look like their predecessors (apart from minor changes like USB3 ports) --- in fact people expect it.
So for iPhone and iPad. Might Apple keep using the same iPhone4 chassis for the next two years, with only minor changes? Why not? There's no obvious improvement it needs.
(Except, maybe, a magnet on the side like iPad has, so you could slip a book-like case on it that covered the screen, and switched it on by opening the book.)
Likewise for iPad.
New must have features in phones/tablets (NFC? near-field charging? waterproof? built-in projector like Samsung Beam?) might change things. But absent those, really, the issue is not "Apple uses two year design cycles", it is "Apple perfects the design, then sticks with it".
mr_ripley - Thursday, March 29, 2012 - link
"In situations where a game is available in both the iOS app store as well as NVIDIA's Tegra Zone, NVIDIA generally delivers a comparable gaming experience to what you get on the iPad... The iPad's GPU performance advantage just isn't evident in those cases..."Would you expect it to be if all the games you compare have not been optimized for the new ipad yet? They run at great frame rates but suffer in visuals or are only available at ipad 2 resolutions. The tegra zone games are clearly optimized for Tegra while their iOS counterparts are not optimized for the A5x, so of course the GPU advantage is not evident.
This comparison does not seem fair unless there is a valid reason to believe that the tegra zone games cannot be further enhanced/optimized to take advantage of the new ipad hardware.
I suspect that the tegra zone games optimized for A5x will offer a tangibly superior performance and experience. And the fact that the real world performance suffers today does not mean we will not see it shortly.
Steelbom - Thursday, March 29, 2012 - link
Exactly this.