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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ananduser - Thursday, March 29, 2012 - link
Imagination does own the fastest GPU available today. The current Tegra offerings cannot match it but nvidia goes a different way. They will start piling CUDA cores like they do on the desktop GPU front. Say you'll have in the future a better quad core from Imagination and nvidia's GPU will consist of something like 64 CUDA cores.zorxd - Thursday, March 29, 2012 - link
The problem is that you can't plug an iDevice to a computer a transfer files as you would on a USB thumb drive without iTunes. That's a major disadvantage.Also if you excluse Apple's SoC, what company makes better mobile GPU than Nvidia? The Mali 400 MP4 is good too (about on par it seems), but I wouldn't say that Tegra 3 is the bottom of the performance barrel. You seems to forget the major players of Qualcomm and TI.
darkcrayon - Thursday, March 29, 2012 - link
You can however transfer files to any number of apps via WIFI or with cloud solutions without needing iTunes though. I'd call it a "disadvantage" but not a major one.You're right the Tegra 3 isn't, I was speaking more generally considering how the Tegra 2 performed vs. the competition as well. It just seemed out of place to choose a tablet because you "love nVidia GPUs" when nVidia has not necessarily put out a spectacular GPU in any ARM SoC.
merajaan - Wednesday, March 28, 2012 - link
You guys must be commended on this review. You covered all the areas that I wanted to know about and really didn't leave one stone unturned. I applaud the depth and detail and appreciate that you didn't rush your review out for launch day like many other sites. I also appreciate the unbiased nature in which the review was written and your honest viewpoints!Anand Lal Shimpi - Thursday, March 29, 2012 - link
Thank you for the kind words :)Take care,
Anand
repoman27 - Thursday, March 29, 2012 - link
So you've gone and included a lovely example of how the AnandTech icon looks at 72 and 144 dpi... How's about including <link rel="apple-touch-icon" sizes="144x144" href="icon144.png"/> on this site so we can have a proper icon when we add an AnandTech web clip to our home screens?adrien - Thursday, March 29, 2012 - link
Still reading the review (and liking it), I'm wondering about thermals.What was the temperature of the room? Could you try with different room temperatures? (I'm wondering how it'll change when it gets 15°C hotter and how it'll fare with sun shining on it).
Is there CPU or GPU throttling when it starts heating? Do you know the SoC temp?
Thanks. :-)
Anand Lal Shimpi - Thursday, March 29, 2012 - link
The ambient temperature in the room was approximately 23C. An overheating condition will trigger an OS-wide warning, which I believe causes the system to shut down.I unfortunately don't have access to anything that could read the SoC temp.
Testing at different room temperatures is an interesting idea but one that would be difficult to accurately control without some serious equipment. I ran these tests side by side at the same time to avoid issues with a changing ambient temperature.
Take care,
Anand
adrien - Thursday, March 29, 2012 - link
Ok, thanks. With summer approaching (and very quickly in France), I guess we'll see real-world tests for the temperature in a few weeks anyway. ;-)scribby - Thursday, March 29, 2012 - link
Nice review :)I'm also wondering about thermals,
What was the brightness level when measuring the thermals on the new ipad?
Thank you.