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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  • zappb - Saturday, March 12, 2011 - link

    Give me a mac book pro with windows 7 as a base install, and id be all over it.

    Mac OS sucks ass, don't know how anyone can make any money using it. Windows or ill stick to lenovo, would rather send my hard earned dollars to apple but as it stands, not a chance.
    Reply
  • bymi - Saturday, March 12, 2011 - link

    Hi,

    thanks for the great review of the new MacBooks!
    I googled a lot, but was not able to find a working copy of the MSR Tools used in his article.
    Sorry if this hat been discussed before, but i didn't find anything using the search funtionality here.

    So where can i get these MSR Tools?

    Thank you everybody for a link.

    Best

    bymi
    Reply
  • Ryan Smith - Sunday, March 13, 2011 - link

    http://www.insanelymac.com/forum/index.php?showtop...

    Note that it only works with Snow Leopard booted up in to 32bit mode, as the driver needed to read the MSRs is 32bit.
    Reply
  • philipus - Saturday, March 12, 2011 - link

    Does anyone know the approximate battery life when using Photoshop (I have CS5) with the dGPU enabled vs disabled?

    What is the approximate performance drop in Photoshop when not using the dGPU?

    These are my main questions before deciding to get the 15" MBP.

    Thanks for any insight.
    /p

    http://philipus.com
    Reply
  • fcarnival - Sunday, March 13, 2011 - link

    Hello Anandtech, thanks for the Apple's revenue breakdown. Could you also post the profit breakdown of Apple's products? I would like to know which device brings the most profit to Apple. Thanks! Reply
  • macfanpro - Monday, March 14, 2011 - link

    I am very curious about this as well - with the tablet market supposedly tripling this year, I want to know what the ramifications are for earnings.

    Apple has a very nice page with related data (http://www.apple.com/investor/), but alas, I don't think they provide earnings breakdown by product (it's not in their detailed 70+ page annual report)...
    Reply
  • amanrai - Monday, March 14, 2011 - link

    could you confirm, definitively, whether or not the thunderbolt port will be able to support a discrete pci e based graphics card with or without a HDMI combination?

    thank you for all of your reviews. they are incredibly detailed and very helpful.
    Reply
  • macfanpro - Monday, March 14, 2011 - link

    Thanks so much for such an insightful review! I'm trying to rationalize buying a MBP, and I have two questions:

    Question about power draw) The MBP comes with a 85W adapter, but its maximum power draw is 93.2W. Could this lead to throttling/maximum performance not being achieved even when one is on the adapter?

    Question about turbo boost) Some people have reported the turbo boost (for the i7 MBP 13) not working in Boot Camp. (Link: http://www.pcpro.co.uk/blogs/2011/03/10/apple-macb... Do you have any more news on this front?
    Reply
  • anaboo - Monday, March 14, 2011 - link

    Strong article - appreciate the in depth of benchmarks and insight.

    I'm hoping you guys can run the same set of in-depth Windows gaming benchmarks on the 15-inch MBP (particularly for the radeon gfx card). Curious to whether there is sub-optimal performance against a similar set of comparables (2010 MBPs, the Mac versions of these games, etc.).

    Thanks!
    Reply
  • davidglennbailey - Wednesday, March 16, 2011 - link

    Best article on the internet on the new Macbook Pros. I'm ordering a 17" Macbook Pro on Friday. Here are my issues.

    1. Just take the cheap SATA hard drive now and upgrade to a fast SSD in the future when the prices fall a little farther? I will probably void a warranty? How difficult is the process to change one of those out and my chances of screwing something up? How do they even connect inside the machine and how reliable is it?

    2. I can understand increased functionality spread out over the life of a product, but even at 3+ years is the .1ghz for 250$ ever worth it? Maybe for the increased cache or any other features?

    3. Upgrading the memory was a breeze last time and shouldn't be an issue. Would there be any point or would it be even possible to go above 1333mhz or 8 gigs?

    Just to add my 2 cents into the debate. I've had this Macbook Pro for about 5 years. I've put it through hell and back. Sometimes, you just wind up getting what you pay for. Great time to buy if you've been waiting for the quad cores for a while.
    Reply

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