The Google Nexus 9 Review
by Joshua Ho & Ryan Smith on February 4, 2015 8:00 AM EST- Posted in
- Tablets
- HTC
- Project Denver
- Android
- Mobile
- NVIDIA
- Nexus 9
- Lollipop
- Android 5.0
Battery Life
It goes without saying that battery life is one of the most important aspects of a mobile device. After all, a mobile device isn’t really mobile if it can only be used for an hour before running out of battery. In order to test this, we turn to our standard suite of battery life tests, which include our web browser battery life test, along with some compute-bound benchmarks to characterize battery life across various use cases.
However, as the Nexus 9 introduces such a unique CPU architecture, I felt that it was necessary to try and adequately capture the full extent of battery life. To this end, I’ve introduced a new test that is really quite simple but important, as we can start to separate display power from everything else since it can often be the single largest consumer of power in a test. In order to do this, everything that could run during a test is disabled, and the device is placed in airplane mode with the display at 200 nits. A white image is displayed on the screen from a full charge until the device shuts down.
Interestingly enough, the display runtime on the Nexus 9 is about as good as it gets when compared to other devices for which we have data. I suspect we’re looking at the direct result of the large battery combined with an efficient display, as the Nexus 9 can last as long as 15 hours in this test compared to the iPad Air 2’s 10 hours.
Unfortunately, the massive lead that we saw with the pure display test is significantly eroded in our web browser test. Our web test is primarily focused upon CPU, connectivity, and display efficiency. Seeing as how the Nexus 9’s display is far ahead of the iPad Air 2 and connectivity should be broadly similar in power efficiency, it seems that all of the efficiency gains from the display have gone into powering the Denver CPUs. It’s likely that process has a significant effect on this, so the more valid comparison is between SHIELD Tablet and the Nexus 9. At any rate, the Nexus 9 does manage to deliver solid battery life performance in this test which is definitely a good thing.
When we move to our pure video test, the Nexus 9 does have a minor regression when compared to the Nexus 7 (2013) and SHIELD Tablet. In this case, the AMOLED displays on the Galaxy Tab S line make for an easy victory due to the relatively high amount of black displayed in the content. The gap is closed between the two devices though, due to a reduced focus on SoC power.
While our web browsing test can give some idea of efficiency, there are often cases where more compute is directly used to support a better experience. To try and test for these compute-bound cases, we use Basemark OS II’s CPU battery life test and GFXBench’s T-Rex rundown for a GPU battery life test. As with the web browsing tests, these are run at 200 nits to keep things relatively equal.
In Basemark OS II, the Nexus 9 does a surprisingly good job as the CPU manages to keep incredibly high sustained performance. The large battery and efficient display seem to help to a significant extent.
In GFXBench, it seems that not much changes overall. The GPU is definitely more power hungry than the PowerVR Series 6XT line-up and sustained performance is noticeably worse, but it’s in line with the SHIELD Tablet. End of run performance ends up a bit lower, but higher than one might expect. This is likely due to differing ambient temperatures. In practice, skin temperatures are about 45C in this test and localized to the top half of the device, and it’s likely that internal temperatures are around 80C as well. Seeing as how Tegra K1 can theoretically draw 33W in platforms such as the Jetson TK1 dev board with active cooling, it's incredibly impressive to see NVIDIA effectively keep such a powerful SoC within the constraints of a passively-cooled tablet.
Charge Time
While battery life is one part of the equation, charge time is an equally important aspect of overall battery life. To measure this, we measure the time from when charging begins to when the device reaches 100% charge. This is confirmed by taking measurements at the power outlet to make sure that power draw is below a certain level.
In this regard, the Nexus 9 is merely average for a tablet, although it does fall behind the competition as it uses a 5V, 1.5A charger for 7.5W instead of the 12-15W chargers that we’ve seen recently. It shouldn’t be a big issue, but in general this does mean that devices like the Galaxy Note 4 are actually better at battery life overall when compared to most tablets.
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AbRASiON - Thursday, February 5, 2015 - link
LCD, not OLED? Blacks being grey? Nope :/blzd - Friday, February 6, 2015 - link
I'd actually rather grey blacks then the loss of detail in black areas. Pure black is nice, but not when it comes at the expense of shadow details.techn0mage - Thursday, February 5, 2015 - link
I agree that late is better than never. Rather than discuss things that can't be changed, I felt the following points were worth raising:Is there any Nexus 6 data in the benchmark charts? I didn't see any. The N6 and N9 were released roughly around the same point in time, and like the N5 and N7 they are high-profile devices in the Android landscape, so it would have been nice to have them in the charts to make comparisons. Please correct me if I've overlooked anything.
The Denver deep dive, while certainly relevant to Nexus 9 and good AT content on any day, was probably a good candidate for having its own article. I believe it is fair to say the Denver content is -less- time sensitive than the overall review. Hopefully the review was not held back by the decision to include the "DDD" content - and to be clear right now I have no reason to believe it was.
WndlB - Thursday, February 5, 2015 - link
Particularly in this kind of full-dress review of high-end devices, could you start covering the delivered sound, the DAC chips and headphone jack?Via A-B comparisons, I'm finding some real differences and, as people go to more high-quuality audiio streams (plus video sound), this is becoming a differentiator of significance. Thanks.
JoshHo - Tuesday, February 10, 2015 - link
We could do subjective opinion, but properly testing 3.5mm output requires significant investment in test equipment.name99 - Thursday, February 5, 2015 - link
I know this isn't exactly a Nexus9 questions, but how can your battery life results for iPad Air2 be so inconsistent?We are given 10.18 hrs for "display a white image" and 13.63 hrs for "display video". For an OLED display this is possible, but not for a LED-backlit display unless you are running the video at a "base-level" brightness of much lower than the 200 nits of the "display a white image", and what's the point of that? Surely the relevance of the "display a white image" is to show how long the display+battery lasts under normal usage conditions, not when being used as a flashlight?
My point is --- I am guessing that the "display a white image" test utilizes some app that prevents the screen from going black. Do you have confidence that that app (and in particular whatever tickling of the OS that is done to prevent sleep) is doing this in the energy optimal way, on both iOS and Android?
JoshHo - Tuesday, February 10, 2015 - link
I don't believe there was any real background CPU usage. To my knowledge the difference is that Apple enables dynamic contrast in movies.easp - Thursday, February 5, 2015 - link
"The successor to the Nexus 7 was even more incredible, as it pushed hardware that was equal to or better than most tablets on the market at a lower price. However, as with most of these low cost Nexus devices not everything was perfect as corners still had to be cut in order to hit these low price points."So, hardware that was equal or better, except it wasn't? This is a situation where being more specific would help. My guess, when you said equal or better you were referring to certain specifications, certain obvious specifications like core count, RAM, and maybe screen resolution?
mkygod - Friday, February 6, 2015 - link
Owned a Nexus 9 for almost 3 months. I purchased three actually to see if backlight bleed was any better, but nope; so I ended up returning them a couple weeks ago. The bleeding was pretty bad; worse than any LCD device i've ever used and definitely worse than the Nexus 5 and Nexus 7. And it would've been okay if it had uniform bleeding like the Nexus 5, but it had blotches of bright spots all along the edges which is even more distracting. I found the reflectivity with the screen a non-factor in my exclusively indoor use. It's a shame because the Nexus 9 is an otherwise damn good tablet. What's also disappointing, as the review points out, is if you want a high-end tablet around this size, your only options are the 9 and the Tab S. It seems like a lot of really good Android tablets are in the 8" size, such as the Shield and new Dell Venue, with more manufacturers on the horizon making tablets in this size.MartinT - Friday, February 6, 2015 - link
I wonder what level of load penalty is incurred by having to ship in optimized code from main memory. Is there any prefetching going on to preposition code segments in lower level caches ahead of being called?