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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  • Wolfpup - Friday, March 11, 2011 - link

    Just LOOK at that. Visually it just makes things look worse...looks like it's taking up space for maybe two more cores, or a fifth core and more cache, or something.

    The only good thing about it is it may help AMD get back in the game. Assuming Bulldozer ends up relatively competitive, AMD's going to be able to have more cores or cache in the same die space, or else have a smaller CPU with the same performance.

    Personally I'm a big fan of Intel's rock solid stability, but it feels like AMD gets better and better with that, where they feel like a real competitor now, and I'd love to see them get parity with Intel or even surpass them!

    To people who have called the higher end config's GPU "high end", it's not. It's a decent mid range part. For the price it ought to have better...maybe that on the low end config and an 800 core part on the high end config (or a Geforce GTX 460), but at least it's a big jump up from the last gen models.
    Reply
  • Belard - Saturday, March 12, 2011 - link

    UH... and what reliability issues are you talking about with AMD? What, intel never screws up? I buy, own and sell both brands. Reply
  • Wardrop - Friday, March 11, 2011 - link

    To be honest, I'm somewhat surprised that Apple don't offer a solution for reducing cable clutter, given their minilast design of the iMac, etc. A docking station sounds like an obvious solution. I'm sure Apple could come up with a really elegant way of docking your Macbook, or otherwise, just connecting all your cables via one main connection.

    I envisage a magnetic solution. You could either have a docking station, where the Macbook sits on something (a stand would be nice). Otherwise, a breakout box type of device, where you plug all your audio, USB and display cables into it, and then attach the breakout box to a single interface on your Macbook, whether it be a plug on the back, the side, or even a magnetised strip on the bottom of the notebook?

    I use my Macbook Pro primary as a desktop. It goes through my desktop KVM, to which my Windows desktop is also connected. I try to avoid unplugging my Macbook from my desk however, simply because it's a hassle. I not only have to unplug the cables, but I have to eject my external time machine drive. One of the most annoying things I find however, is that because the screen resolution on my MBP is significantly lower than my desktop monitor, it often screws up all the windows. I find I need to spend time resizing all my windows for the 13" MBP display, and then have to do the same when I connect it back up to my 24" desktop monitor. When you've got 10+ windows all perfectly arranged to suit your working style, it's a major pain, hence I avoid taking my MBP off the desk.
    Reply
  • tzhu07 - Sunday, March 13, 2011 - link

    I was thoroughly unhappy with the current offerings for a docking station for my late 2006 macbook pro, and so I decided to go to home depot and build one myself. And I made it super elegant and wirefree. Also helps that my monitor is connected to an arm, keyboard wireless, and also mouse is wireless too.

    http://www.majorindulgence.com/file_exchange_data/...

    ahhhhhhhhhhh.....super clean
    Reply
  • bronze5420 - Friday, March 11, 2011 - link

    this is definitely the best computer review i have ever read. very informative. answered all the questions i had and then some. keep up to good work. and does anybody know if OSX Lion will feature TRIM support for third party SSD's? Reply
  • 13579abc - Friday, March 11, 2011 - link

    First let me echo the sentiment of gratitude expressed throughout this forum. AnandTech really is a cut above other tech sites.

    Second, if I may add my two cents, heat and noise are such an important part of the mobile experience that they might deserve a little additional attention in this review, particularly given that apple tries to differentiate itself from competitors in these areas. This review touches on the surface temperatures of these new Macbook Pro models, but I wonder if there are any plans to more thoroughly examine surface temperatures in different areas of the notebook (i.e. palm rests, keyboard, bottom surface…). Also, does AnandTech have any comment on the effect of inappropriate quantities of thermal paste reportedly used in the notebooks? Some forum posts report amazing thermal improvements resulting from properly applying new thermal paste, but to be honest I have some doubts regarding the validity of these posts and think that they might be misleading.

    Along similar lines are there any plans for a quantitative analysis of the noise output from these new models.

    Again,thanks for a great review.
    Reply
  • tipoo - Saturday, March 12, 2011 - link

    Seconded, some numbers on thermals and decibels would be nice. Reply
  • Balfa - Saturday, March 12, 2011 - link

    I've just bought the new 17" that I use mainly for software development but even at 1920x1200 it is a little on the cramped side. So at home I connect it to a Cinema Display 27'' via mini DP cable to the new combo TB-MiniDP port. And the monitor cable use also a Magsafe connector and lastly a usb2 for camera, sound and 3 usb ports at the back of the monitor like most folks already know likely.

    Now what I really wish for the future Apple is extends that paradigm of a monitor-docking station with a new 27'' monitor with only the Magsafe and one Thunderbolt cable. At the back of the monitor implements every ports that could be needed: USB3, FW800 (1600 maybe why not), eSATA (unlikely I know). And lastly add a powerful discrete GPU in the monitor itself with a quick access door to upgrade it if needed. That way you could remove the one in the MBP for lower cost and better battery life and still have a powerful GPU solution at home for gaming, transcoding and the like.

    I think the monitor is the best place for docking a laptop, not needs for a separate device. I already put all my external disks behind it anyways (I place my monitor in the middle of the desk so there's a lot of empty space behind) and it will be the shortest route to plug them, less clutter that way. Gee it's a great idea isn't it!
    Reply
  • MrBrownSound - Saturday, March 12, 2011 - link

    Once again anandtech pulls off a amazing review. With this information I can cofortably say I will wait for Lion to come out. Reply
  • ProDigit - Saturday, March 12, 2011 - link

    None of these machines is worth their price!
    The 13" has a price of a 16" laptop
    Reply

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