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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  • dqnet - Wednesday, March 16, 2011 - link

    I'm really considering splashing out on the 13" but I've read countless articles and all I hear is the glossy screen is either horrible or awful. I don’t want the 15", I need the portability and I don’t know what on earth to do!??????????

    Then comes the SSD issue, if I want this option I have to wait 6 weeks!
    I can always get this later down the line I guess?? Well from what the article suggests??

    Any help (opinions) would be great as right now I’m lost! :(
    Reply
  • Mac Ike - Wednesday, March 16, 2011 - link

    If a person bought a MacBook Pro in the last 18-24 months,I don't see the reason to upgrade unless you're on the Bleeding-edge of performance needs and Mac your living with your Mac. Many Apps and advanced Software aren't even optimized to take advantage of multiple Cores,or Hyper-Threading/Turbo Boost. I don't care as much for Auto Switching Graphics,since I have total control of my Graphics with my March 2010 MacBook Pro 17"/Core 2 Duo/2.8 Ghz/4GB RAM/AG/500GB HD/512MB or 256(IG) VRAM-dual cards/express card. if I was buying new today,Hyper-Threading and Turbo Boost schemes would be OK,but there's no way that I'd trade or sell my machine for these updates! To me,speed hasn't been an issue in 2 or 3 years! My 2006 20" iMac was at 2.0 Ghz,and the newest Macs are 2.0-3.0Ghz or so. I know that Sandy Bridge is faster than a Merom Core Duo,but most improvements seem to have come from adding more Cores and RAM,so that more tasks can be done simultaneously! I don't care for gimmicks,Turbo-Boosting,Hyper-Threading,and poorer graphics to convince me to upgrade my Macs. Unless you are a Digital Video Content Creator,or other high-powered user,or your Mac is 3 yrs. Old or so,you should Max-out your RAM,get a faster HDD or an SSD,rather than buying a Whole New Mac! If you have the money to spend,good for you,but a combination of Power,Battery-Life,and Portability,are the REAL issues! I wish people would stop telling others that they're Idiots for paying Mac prices,since it's our Money,and only YOU can determine what's good value for the Performance,elegance,and Stability of Apple Hardware! Reply
  • rredge - Thursday, March 17, 2011 - link

    Today, the local Apple store acknowledged that my 15" MacBook Pro is not functioning properly and refunded the purchase price despite the fact that I was just past the 14 day return period.

    The problem is that the computer ceased to respond to the trackpad even when rebooted with the power button.

    In the course of trying to figure out what the problem was, I discovered that there are reports of people experiencing similar problems for all three models (13", 15", 17") on Apple's support forum, where one thread alone now runs 19 pages, as well as elsewhere on the internet.

    The Apple store personnel told me that Apple has not acknowledged that there is a problem with this line of computers, although they acknowledged in less than two minutes that my computer has a problem sufficiently serious to warrant a refund out of the return period. I declined a replacement because they expressed ignorance of the issue, indeed said that Apple did not acknowledge an issue, and were unable to give me any assurance that a replacement would perform any better.

    The questions at this point are how widespread this freezing problem is and whether Apple is going to acknowledge it and fix it.
    Reply
  • rredge - Thursday, March 17, 2011 - link

    The second paragraph should have said that the computer ceased to respond to both the trackpad and keyboard. Reply
  • nitrousninja - Thursday, March 17, 2011 - link

    I saw the benches but I dont know if that translates into a big real world difference in SSDs. I'm mostly doing stuff in Word/Excel, some light video editing/converting, and occasionally some WoW. This would be in the base model 13"

    Should i go with the stock 3GB 128GB SSD or the OCZ 6GB I can get at Microcenter and install it mysel?. I've never done that on a Mac.

    Thanks for the help!

    Matt
    Reply
  • tno - Wednesday, May 04, 2011 - link

    Doubt you're still wondering but, if you want to have any space left after installing an OS and still want an SSD then you should splash for the 128GB SSD or wait till a reliable larger SSD is available. I wouldn't go less than 120GB.

    As to whether you should get an SSD, just ask yourself this question:

    Have you ever sat, even for a moment, and wondered why an otherwise well specced (but magnetically driven) computer seemed slow?

    If yes, then you'll likely be able to set that question aside by putting in an SSD.
    Reply
  • tranksen76 - Friday, March 18, 2011 - link

    Hello Rredge,

    how frustrating your experience sounds!
    2011 was the year I was finally supposed to buy myself my 1st ever MBP after 18 years in the Windows environment.

    It took me long enough to choose between a 13-inch or 15-inch one but then I started reading about these freeze issues a lot of users have been facing. being French i only heard about this problem within French forums and i was hoping this would have to be a specific problem for a batch of units delivered in France but now I have to admit this really is a larger scope problem.

    For what it's worth there were comments on the forums I went through about I-Stats being a cause for these problems as it installs by default with a settings that take over the fans control.
    Did you have that app on your computer?

    Best regards
    Tranksen
    Reply
  • rredge - Friday, March 18, 2011 - link

    Bonjour Tranksen,

    The fan on my computer was acting normally when this happened and I do not have that widget installed. I was running Terminal, TextEdit and Safari and the processor was under extremely light load.

    You will find a good deal of discussion about this problem on the Apple U.S. support forum at http://discussions.apple.com/category.jspa?categor...

    This is not an imaginary issue. Apple agreed to the return of my computer for full refund despite it being outside the 14 return period.

    I would consider repurchasing one of these computers, but not until Apple clarifies what the problem is and fixes it.
    Reply
  • tipoo - Saturday, March 19, 2011 - link

    You said that noise was an issue with the larger MPB, but I'd like that to be quantified in decibels and compared to other laptops in a table, in future reviews. Reply
  • Omid.M - Monday, March 21, 2011 - link

    Can the AT team comment on this please:

    http://apple.slashdot.org/submission/1504006/2011-...

    Click on "Link to Original Source"

    Can you guys duplicate this issue? Is it just simple overheating and poor design on Apple's part? I really want to know...

    Also tweeted to the three of you. Thanks for your thoroughness, gang.
    Reply

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