The dGPU: Killing Battery Life

The 15 and 17-inch MacBook Pros have a discrete GPU that only turns on if you fire up an application that really needs it—at least that's how it is supposed to work. In practice, the discrete GPU takes over control if your application uses any one of a number of frameworks—and some of the time, the dGPU simply isn't necessary.

Case in point, launching Chrome won't trigger a dGPU switch but the moment it encounters Flash the discrete GPU will take over. The bad news is that even if you close all Chrome windows, the dGPU won't power down until you quit chrome entirely. The same is true for Photoshop. Launch the application and you're still on the iGPU. Actually open up an image and the dGPU takes over. Even if you close all open images and just leave the Photoshop application open, the dGPU won't relinquish control. FaceTime and anything using the integrated camera also require the dGPU, despite it being totally unnecessary.

If you connect any external display to the 15 or 17-inch MacBook Pro that also forces the dGPU on, at which point both the integrated panel and external display are driven by the dGPU. There is no funny frame buffer copying going on, both the integrated and discrete GPUs have their own connection to the display.

Apple also fails to provide a way of turning off the dGPU by default—the best you can do is shut off the iGPU and just use the dGPU entirely. Thankfully Cody Krieger's gfxCardStatus tool gives us exactly what OS X does not. Version 2.0.1 adds support for the 2011 MacBook Pros.

I'm going on and on about the dGPU because it's state can seriously impact battery life. The numbers below should help put that in perspective for you:

Impact of Discrete GPU on Battery Life
15-inch 2011 MacBook Pro Light Web Browsing Flash Web Browsing
Integrated GPU (Intel HD 3000) 8.85 hours 7.03 hours
Discrete GPU (AMD Radeon HD 6750M) 5.67 hours 2.97 hours

Even just browsing the web, the dGPU being on drops battery life by 35—60%. Under full CPU load I suspect the percentage difference would be smaller, but still significant. The worst part of this all is that without gfxCardStatus you can negatively impact battery life by doing something completely innocent like accidentally leaving an application open. Given how much OS X is tailored to simply closing windows when you're done with them and not quitting applications, an overly aggressive dGPU can really be an issue.

Thankfully we do have gfxCardStatus but there's honestly no reason Apple shouldn't include this functionality with OS X from the start.

The GPU Comparison Display Quality
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  • claytontullos - Friday, March 11, 2011 - link

    The laptop was not constantly crashing, maybe 1-2 times per week. Had I sent it in to them nothing would have happened because they would have run their own woefully inadequate ram test. I replaced the ram and have not had any crashes since.

    HP also insisted that I reinstall vista when my led screen turned solid blue at a certain angle.
    Reply
  • alent1234 - Friday, March 11, 2011 - link

    i've been dealing with computers long enough to remember lifetime warranties being standard and dell sending replacement parts with no questions asked.

    around 2000 is when it changed and i've had to lie to tech support even when i called for large customers with tens of thousands of dell computers bought.

    my own personal experience with HP tech support for a work laptop vowed me to never buy a HP laptop again unless it's from costco or dirt cheap to where i can buy one every year and junk it without thinking twice.

    same with dell. 7 years ago i bought a $1500 laptop with the 3 year warranty. 2 years into it i find out the battery is not covered. Unlike with Apple where the entire laptop is covered and going to the genius bar doesn't mean being on hold for hours and needing a translator to talk to someone
    Reply
  • erple2 - Friday, March 11, 2011 - link

    Huh. I've never had a problem with HP service before. I've had HP laptops ranging from the 2800T to an Elitebook 6930p to an Envy 15. In each case, there was an issue that had to be resolved, and I received prompt, accurate service, including a box they sent to me to ship the device back to them. Yes, they didn't cross ship a laptop, but that's not practical.

    My experience with Apple's Genius Bar, however, hasn't been so rosy. Personally, I'd rather wait on hold in my house for 2 hours than wait around at a Genius Bar for 2 hours for someone to actually help you. Granted, it was crowded, but it's irrelevant to this discussion.
    Reply
  • claytontullos - Saturday, March 12, 2011 - link

    When the problem and solution is crystal clear to even the most ignorant person then HP's service is fantastic: ie: Won't Power On, Disc wont eject, Nothing on screen.

    However with intermittent issues HP's support is horrible. Even speaking with a supervisor nets little reprieve from ignorance.
    Reply
  • argosreality - Thursday, March 10, 2011 - link

    The Envy line comes with its own dedicated support group that is not the usual, outsourced to India group. Quite a bit better. Also, strangely I have seen memory pass the Pc-doctor tests (usually what HP uses outside of the BIOS runs) but fail memtest. Not sure why, could just be different test algorithems Reply
  • starfalcon - Sunday, May 15, 2011 - link

    What kind of 13 inch laptops have discrete graphics anyway?
    Except maybe that smaller Alienware.
    Reply
  • Taft12 - Thursday, March 10, 2011 - link

    <i>My preference would be two cables: one for power and one for peripherals/display. Today, it's five.</i>

    What you've just said is that Macbooks need a Dell Latitude-style docking station option in the worst possible way. Your preference is 2 cables. Mine is zero. Just snap in. (I've had this for over a decade now)

    If Apple is serious about phasing out desktops as you suspect, that'll be something that needs to come first.
    Reply
  • secretmanofagent - Thursday, March 10, 2011 - link

    I've always been hesitant of docking stations. I've had a Dell that for the most part would undock somewhat correctly, and currently have an HP work computer that refuses to undock at all. For me, the convenience has always been hampered by the usability. Reply
  • gstrickler - Thursday, March 10, 2011 - link

    Actually, with MagSafe power and Thunderbolt, that's essentially possible. A dock that includes a connection to both ports could offer Mini-DisplayPort, DVI, VGA, USB, Ethernet, FireWire, eSATA, and Thunderbolt connections, and optionally, even a PCI slot or two. With 4x PCIe compatibility and 20Gb/s bidirectional throughput, a Thunderbolt port has plenty of bandwidth for that. Of course, Apple is currently the only company who could offer it with the MagSafe connection, but a third party could at least reduce it to 2 quick connections. Reply
  • erple2 - Friday, March 11, 2011 - link

    Huh. My windows laptop has only 1 connection that handles mouse, keyboard, monitor, power, ethernet and external storage. 'Course that's the beauty and convenience of a (working) docking station, something that I never really thought was worthwhile until I actually got one.

    I'm bummed that consumer products don't come with one.
    Reply

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