It’s not a placebo effect: this is why your Nexus 6 feels so fast after the Android 5.1 update


nexus 6 overview

Android 5.0 Lollipop is great, but for those on the Nexus 6 there’s no secret there were some troubling performance issues that a phone of its stature shouldn’t experience. We thought much of the issues were due to the infancy of the ART runtime and possibly due to problematic device encryption. We expected much of that to be cleared up with Android 5.1’s arrival.

It was, at least according to some early impressions around the Phandroid office. But what changed to bring about that performance boost, exactly? Google wasn’t keen to go into detail, but renowned kernel developer Francisco Franco gave us a good bit of insight.

Alongside general improvements to the ART runtime as a whole, Google apparently unlocked the device’s CPU to run at full quad-core mode at all times in order to handle task scheduling more efficiently. What this means is that “Job B” no longer has to wait on “Job A” to finish on a certain core before carrying out its task. It can simply jump onto another of three other cores to allow everything else ample time and room to work. Think of it as a one-lane street merging into a multi-lane highway.

Taking things a step further, Google was able to reduce the lag and improve battery life at the same time thanks to disabling a Qualcomm driver that would needlessly boost individual CPU cores whenever tasks migrate from one core to another. Franco says he’d already made these tweaks in his version of the kernel, so kudos to Google for seeing things similarly and following suit.

So if you notice increased performance and improved battery life after upgrading to Android 5.1, it’s not a placebo effect — Google made some significant changes, and the great thing is we haven’t even scratched the surface of what we know to be different in this latest version. Be sure to try Android 5.1 on for size on your Nexus device of choice using one of the available OTA links.

Quentyn Kennemer
The "Google Phone" sounded too awesome to pass up, so I bought a G1. The rest is history. And yes, I know my name isn't Wilson.

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  1. I want some 5.1 in, or around, my mouth as soon as I get home!

    1. Wouldn’t you want it in your phone?..

      1. On his phone?!!! thats too fetishistic for him.

        For him is. In, aroung or kick it out. Right right?

  2. Thanks for the mention :)

    1. Hey bud you always have the best kernels. I miss my Nexus 5 running stock with Franco

  3. Do I have to wait for my carrier to release the update for me or am I unlucky?

    1. you can sideload it :)

      1. That’s like a foreign language to me

        1. I understand….you can always google it. You just download the file on your phone, and do some restartin’ essentially…its not too difficult. Otherwise, yes u are going to have to wait for Google to release it

          1. Yeah I shall take a read. Thanks. I’m obviously just worried about ruining my phone

          2. A Nexus? Ruin? Ha!

          3. Nexus noob alert ⚠

          4. I would recommend the Nexus Root Toolkit from WugFresh then. Everything it does can be done manually, except it will guide you through in flashing new images yourself (instead of waiting for an OTA) and more.

            Don’t worry about breaking anything, since factory images are available and you can always “start over”.

          5. Much respect for your support. Appreciate it

          6. You’re very, very unlikely to brick it with the OTA sideload method. You’d honestly be more likely to lose your head while you’re trying to get all of the prerequisites set up (ADB, etc.). That was the most frustrating part for me.

  4. I hope this is the case for the nexus 9 as well, obviously tweaks to the Nvidia chip instead of a snapdragon chip

    1. Denver is already amazing, I think the tablet issues are more about ART infancy, problems on the Framework etc rather than poor CPU code optimizations.

      1. Ill hold judgement but I have yet to have a good NVidia experience. 3 devices, 3 devices that immediately performed poorly (day to day, not benchmark or single game) compared to qualcomm devices of the same era.

  5. Does it now support hardware encryption?

    1. No.

      1. Thanks Franco :) I hope they will change that in a future update.

      2. has the encryption got disabled on 5.1 ?

  6. “It’s not a placebo effect: this is why your iPhone feels so fast after the iOS update”

    Filed under headlines never to be written. Ever.

  7. CPU running faster, what will this do to battery life??

    1. It said in the article the improved battery life as well

      1. Yes, but I was talking about that specific change, not the overall 5.1 update.

        1. I’d imagine the improved battery life would cover the all the cores firing off when needed. Unless one is playing a game that needs a crazy amount of resources.

    2. Oddly enough, likely improve it.

      Its not that its running faster, as if its overclocked. What they have done is basically allow it to run more efficiently. The work is the work, if you need 3 computations done then you need 3 computations done. What they have changed from is having one person compute all 3 and having 4 people share the load. It gets done at least 3 times faster (and often a bit extra).

      So the result is the CPU does it 3 times faster and, as a result, is working 1/3 as long. The faster it does it the fast it can go back to napping.

      1. Cool, I appreciate the discussion

  8. Been happy so far today. I’m at 73% battery after 10 hours use and 1.5 SOT. Its very smooth and fast.

    1. Good lord, after 10 hours and ~1 SOT i’m usually at like 40%. I just updated to 5.1 this afternoon hopefully I get a moderate improvement. Can’t expect that level though, I’m guessing I have a lot of apps eating up battery here and there. Ditto on the smoothness though, it’s WAY better for me.

  9. still waiting for the update on tmobile

    1. Download the image direct from google. The instructions are right on the page on how to load it. Running 5.1 on T-Mobile now!

      1. If I apply the image will I loose all my data?

  10. I wonder/hope these optimizations make their way to the Nexus 4 version of the update as well. Mine isnt bad but there is the occasional stutter, especially in the browser, that could be taken care of.

  11. If I could get it to side load on to my N6 I would love that. However there seems to be a bug were it boots you out after a certain percentage. Something about the partition having unknown components in it.

    1. If you were rooted it will boot you out of the sideload process at around 47%

      1. I’m not rooted though. Its driving me nuts lol

    2. If you have a custom recovery I’d recommend giving this a shot:

      I came straight from full stock (with custom recovery) and just wiped dalvik and cache, flashed new bootloader/radio and easy peasy

      1. Since you only wiped dalvik and cache did you manage to keep all of your user data? I ask because in the past I’ve only rooted for Xposed and have neglected ROMs, which would be a reasonable means of updating if it meant avoiding full wipes/factory resets.

        1. Yep, didn’t wipe data at all, it just took a while in the “upgrading apps” screen when it first booted but all my apps and data were just as I left it before

          1. Excellent. I’ll likely give this a go. I appreciate the information and reply.

  12. My nexus 6 has been flying after this update. 5.1 is what 5.0 should’ve been. Now I don’t feel like I’m running a beta os anymore.

    For those that want an easy way to update, visit this website: http://syedzain7.blogspot.in/2015/03/how-to-flash-android-51-on-nexus-567910.html

    1. Still horrible volume control?
      That change has been the bane of my existence with lollipop.

      1. Yea unfortunately.

        1. well you can install this app for nicer control of the volume:

    2. heh i was thinking this on my drive home today. 5.1 should have been the first release of lollipop. but then i thought, eh, i’ve gotten to use my beloved n6 for these past four months, so it was a pretty good tradeoff…

    3. The help is great, but like i posted, i’m almost certain that using the google pkg on a rooted N6 will crap out at like 30% or so. I could also be nuts. The only 2 phones i haven’t rooted have been my N1 and this N6 because i wanted clean easy fast OTA’s, but i have no patience tonight since some are saying they’ve received their N6 T-Mobile 5.1 OTA
      Just wanted to repost this from the above article so i don’t seem completely loco:
      “OTA links for each of those devices are now available to flash atop your existing installation. Note that these should only be flashed on top of the appropriate firmware (listed next to each file) and that you might need to be on stock firmware (meaning no root or custom ROMs) for the best result.”

      1. You can flash just the system.img and boot.img (boot is to get the newly tweaked kernel) from the factory images and only need to re-root after the process. This can be from any version of the software.


  13. I HAVE A DAMN DREAM that one day when google releases an update, EVERY android user could update to the latest OS on THAT DAY.. lol i just laughed at myself for having hope for such a thing ..

    1. Silly guy… this isn’t Apple or WIndows Phone… you gotta wait your turn.

      1. If you even GET a turn that is…..

        1. That’s true… Very true actually.

    2. You mean like how windows can update on every pc regardless of if it’s running with an AMD or Intel CPU, and regardless of the brands of other hardware as well? Would be nice if this was possible.

      1. That’s different. All windows software is the same. All android is the same inside except the OEMs like Samsung or htc are the ones that are taking long for the update, they probably get the updates the same as everyone else, but their developers are the ones tweaking stuff and adding layers on top. Once they get the updates optimized for their skins, then they release it over the air. I have a nexus device so I don’t have to wait. I like getting updates before other people lol. So I don’t have the same problem. Don’t blame google. Nexus users get the updates themselves from google because it’s google’s phone. But Samsung users for example get their updates from Samsung after Samsung does stuff with it. That’s why you would get it at a different time. Again google pretty much gives everyone the update at the same time. But you have to go through your middle man first which is an OEM. Nexus users don’t have a skin, so no middle man. Meaning we get it first and basically at a different time.

        1. Can you even imagine a Samsung Galaxy Note without going through the features that Samsung adds to the OS? Especially for the S-Pen.

          1. A lot of the note features, I like, and a lot I don’t need. My point is that with all those features that they add, useful or not, makes their software updates come later as a result. But I figure the trade off for a bigger screen and front facing speakers, and timely updates are very important selling points for me. when I get an update in android version, I asociate that with new software from developers who make custom roms or xposed modules.

      2. yeah, cause with windows they add drivers for all hardware that a manufacturer submits and tests. that’s why your OS on your computer fills 30 GB of harddrive space. since most mobile phones don’t even have 30GB of fixed memory this isn’t possible. a hardware manufacturer makes their own drivers for the hardware and release the OS when they have tested that hardware with their OS package.

    3. Well, talk to the OEM’s who make changes to the underlying and background functions of Android for their own devices.

      Just how things are when it comes to an open source OS.

    4. Yes exactly as Apple does. That’s one thing I really miss. :(

    5. Those who really want the update immediately can flash the factory image or install the OTA zip. Google has explained many times the reason they release updates like they do.

  14. Damn…and the Z3 is barely getting 5.0.2

  15. So, is this improvement for all qualcom processor devices? Like the M9 for example?

    1. You’d need a custom kernel for it. I think I have a faint idea of which drivers are in question but yeah, custom kernel

      1. Just because Franco commented on it doesn’t mean you need a custom kernel. Re-read the article.

        1. Er…that’s not why. It’s because there are custom tweaks that OEMs will probably not introduce. It’s not because Franco commented lol. I work on ROM development and I would know.

          And yeah, you are right that HTC’s kernel is technically a “custom” kernel but I meant an aftermarket one because, like I said earlier, it’s probably not likely that HTC will implement it

      2. well technically, HTC’s kernal would be a custom kernal.

  16. Either I’m way zipped on my cancer meds or I’m losing it. How do I flash this on a T-Mobile N6 that is NOT rooted?
    I would appreciate help or a link. I assume I don’t need any of the usual root tools, but I saw a warning somewhere saying if I was rooted then I might lockup at a certain %.
    Like I said, I might be over morphed, but I want my 5.1 ?
    Just wanted to repost this from the above article so i don’t seem completely loco:
    “OTA links for each of those devices are now available to flash atop your existing installation. Note that these should only be flashed on top of the appropriate firmware (listed next to each file) and that you might need to be on stock firmware (meaning no root or custom ROMs) for the best result.”

    1. It’s available on every Nexus 6 since they’re all using the exact same software and hardware even across carriers.

    2. Stock firmware doesn’t mean no Root or custom ROMs.. Just firmware :)

    3. Everything you need to know and need right here directly from Google:


  17. Call me impressed :) 5.1 stock is perfect.

  18. Can someone please tell me what the latest OTA update is supposed to be, according to my phone it is up-to-date with android 5.0.1. But I thought it should be 5.0.2? Is my phone playing up or what…

    1. Tom, the newest Android version is 5.1 which is still rolling out OTA (Over The Air) to the NEXUS devices listed in the above article.

      1. Why is my device saying I’m up-to-date with 5.0.1? I’m confused lol..

        1. It takes a while, your phone currently says it really. s up to date until Google.sends out the update. So technically your phone is up to date but not really. Just give it time. I’m waiting over here as well. :( ATT Nexus 6

    2. 5.0.1 is the latest before 5.1 for the nexus 6, only nexus tabs (and only the 7 I believe) ever got/will get 5.0.2.

      The next jump for the nexus 6 is to 5.1

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