Battery Life

Of course the next question is how battery life fares, after all, it doesn’t matter too much in a mobile device if we have great application performance but need to be tethered to a charger all day long. Back to those Cortex-A9s, the next part of the picture is what power management features are and aren’t supported. First off, OMAP4 is a synchronous architecture, which means that there’s one frequency plane for both A9s - each runs at the same clock. Both can be clock gated, however.

The important next bit is that each CPU is on its own power domain. The power states of each CPU doesn’t have to be the same, and OMAP4 supports three modes - Normal (run), dormant, and power off. You can see the different power domains as illustrated by the following diagram.

TI also provides a nice table with the supported power states and clock gating states depending on what assertions are made in the local power control module register.

What’s particularly interesting is that we can actually watch cores turn on and off both through console output on the device (by running something like dmesg) and moreover there’s even some nice software that will show us graphically. System Panel (which I’m a pretty big fan of) recently added support for visualizing load on multicore Android devices, and you can see how things fare when there’s both idle activity (CPU1 gets shut completely off), and when I’m generating tons of load by flicking the page around wildly (both CPUs are on, and clocked at 1.0 GHz).


Like most modern SoCs, OMAP4 can dynamically change frequency, however it also can dynamically change voltage with a power management technique called SmartReflex. There are two different modes for SmartReflex, one which consists of an entirely hardware-controlled voltage control loop (class 3) and another which is assisted using software control (class 2). I’ve verified that the Droid 3 is using class 3:

“<6>[    0.000000] SmartReflex CLASS3 initialized”

SmartReflex encompasses both the dynamic frequency, voltage, and power switching functions on the OMAP4430. The aim is to use silicon in the best way possible depending on either static silicon performance (given manufacturing) or dynamically based on temperature induced performance, and raise or lower voltage accordingly. To a large extent, SmartReflex it somewhat analogous to Intel’s SpeedStep and related suite, and in OMAP5 even gains a turbo mode which allows the SoC to temporarily exceed its normal maximum clock.  

Now that we’ve gone over the power features of OMAP4, it’s time to present some Droid 3 specific battery life results. As usual, we’ve run our battery life testing suite on the device. The first set of tests are our page loading suite, which load through a few dozen pages every 10 seconds or so until the phone dies. The backlight brightness is at 200 nits and of course always on, to mimic continual web browsing.

Smartphone Web Browsing Battery Life

The Droid 3 both brings improvements in performance and display resolution alongside better battery life for smartphone web browsing. The other interesting performer to keep eye on is the Droid X2, which includes the same sized battery and baseband (MDM6600), but Tegra 2.

WiFi Web Browsing Battery Life

Next up is WiFi web browsing, where we run the same test but using WLAN instead of cellular connectivity. Here we can’t compare to the Droid X2 anymore as there are different WLAN stacks in each, but the Droid 3 continues to outperform its predecessors.

3G Talk Time Battery Life

Motorola continues to somehow have a secret sauce for continually delivering incredibly long call time battery life, with now five spots dominated by Motorola devices. I’m still at a loss for exactly what they’re doing that gives them such a leg up, but it’s considerable.

WiFi Hotspot Battery Life Time

Finally is the WiFi hotspot battery test, which consists of a single WLAN client loading four tabs of our page loading test (two with flash content, two without), and a 128 Kbps MP3 streaming internet radio station. The display on the device is off the whole time. It’s a heavy test that mimics continual use and keeps everything awake on the device.

Here the Droid 3 does very well, though we don’t have any comparison data from the Droid 2 or Droid 1 due to this being a newer test. The overall results definitely illustrate the potential power savings of a dual core architecture - to put it in Anand’s words, you just can’t beat voltage scaling when dealing with power. 

OMAP 4430 and Performance Analysis Concluding Thoughts


View All Comments

  • EndlessChris - Saturday, July 30, 2011 - link

    Great review as always. Looks like this will be my new phone :) Reply
  • RaistlinZ - Saturday, July 30, 2011 - link

    Sharp lookin' phone. I like. Reply
  • vol7ron - Sunday, July 31, 2011 - link

    I like this too, larger screen, nice looking keyboard, great looking device. It seems to have it all.

    One thing, does it really have a 0.3MP front-facing camera? I would suspect 1.3MP would be more realistic, especially since there are probably economies of scale for that technology right now.

  • Brian Klug - Friday, August 05, 2011 - link


    It definitely does have a 0.3 MP (VGA) front facing camera.

    I'd like to see 1.3 MP sensors on the front for sure, but at this point it doesn't make sense until both the per-pixel quality is the same (same size pixels) and there are apps that can actually do some HD teleconferencing (like if Skype had support). We're almost there though.

  • Myrandex - Monday, August 01, 2011 - link

    It would be for me if it wasn't for this bastardization that Verizon did:

    The obvious next part of the story is that WCDMA HSPA+ 14.4 Mbps connectivity. Unfortunately, Verizon has locked the retail Droid 3 out of seeing USA-based GSM/WCDMA networks with an MCC (Mobile Country Code) lock.

    Why can't Verizon just allow the hardware to perform at its fullest rather than finding some way to lock it down? They have always been terrible about locking their phones in some way.

    Jason Cook
  • themossie - Saturday, July 30, 2011 - link

    Tried the Droid 3 in store the day it came out, mixed feelings about the screen.
    Found it very usable for applications, not usable for serious reading (news, ebooks, etc). First time I've suffered eyestrain from an LCD screen with decent brightness and contrast. Droid 1 works great for this use case.

    Brian, Anand and the rest of the AnandTech team - any opinions on this? Anyone else?
  • themossie - Saturday, July 30, 2011 - link

    Also, thanks for the great review - business as usual at Anandtech! Reply
  • steven75 - Saturday, July 30, 2011 - link

    Indeed. Can't believe he tried to equate this pentile display with less resolution in a larger screen size (significantly worse PPI) with the retina display. They aren't even close. Reply
  • bplewis24 - Saturday, July 30, 2011 - link

    I'll trust the guy who looks at hundreds of phones per year over the hyperbolic masses who troll the internet.

    I'll also trust my own eyes and science, which prove you wrong.
  • Finraziel - Sunday, July 31, 2011 - link

    Well, I'll also trust my own eyes, and the picture right above where Brian says he doesn't mind pentile too much really makes the droid3's screen look like crap compared to the lower resolution droid2 right next to it. My experience with other pentile screens also suggests there's absolutely no point in increasing the resolution only by using a trick like this, you end up with noticably lower effective resolution. I'd prefer an actually sharp screen over impressive specifications.
    I really hope when the 720p screen phones come out in the next half year or so they wont be using cheap tricks like this.

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