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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  • robco - Thursday, March 10, 2011 - link

    I made the mistake of buying a 15" MBP eighteen months ago and am stuck with a machine that has mediocre graphics and overheats constantly. Don't buy the MBP if you actually use it on your lap. That being said, the only reason I bought it over the MacBook was the dedicated graphics. With the awful performance of the Intel integrated chip, I hope Apple releases a 15" MacBook with the option of dedicated graphics for consumers. I'm not shelling out $2199 just to get something with a decent video card. I wouldn't recommend the 13" at all, as there are several alternatives in the 13-14" range that offer dedicated cards.

    I fell victim to the hype and now I have a fairly recent machine that can barely handle SC2 and an iPhone that can't make phone calls. Don't make the same mistake. Most of the tasks you can do on a Mac you can do on a Windows PC. Unless you are actually a pro and need a pro-grade machine, don't waste your money. For those who can justify the expense, they are nice machines, but if you actually put them to work, be ready to set them on a cool surface or get a cooling pad. They run awfully hot.
    Reply
  • KoolAidMan1 - Thursday, March 10, 2011 - link

    My MBP from last year plays SC2 perfectly, above 60fps most of the time which is great. Same with Source games. People on Youtube have already uploaded video playing the Crysis 2 demo on the new MBPs and it looks great.

    Your machine is almost two years old. Be logical when complaining about performance. Just because your machine is slow doesn't mean that the new ones aren't screaming fast: http://www.pcmag.com/image_popup/0,1740,iid=287468...

    The 13" MBP is also decent with the SB IGP. I've seen clips on YT of people playing games even on the slower Macbook Air and it looks good. IGPs have come a long way from where they were in 2009.
    Reply
  • robco - Thursday, March 10, 2011 - link

    I'm a little miffed that a machine that was so expensive has become outdated rather quickly. I paid a lot just to get dedicated graphics. I could have and should have paid less to get a Windows notebook. I won't make the same mistake again. If you're a consumer and don't need a pro-grade machine but still want good graphics, the MBP is a poor value.

    The MBA actually handles games better than the new 13" MBP because it still uses the C2D and the NV integrated chipset. Once it switches to Sandy Bridge, performance will drop as it has with the MBP. The only area the MBA is slower than the MBP is raw processing power, graphics and disk access are much faster.

    With Apple you can get a notebook that performs well, you just have to shell out $2199 to get it. I did that once, I won't do it again. it just isn't worth it unless you're a pro user who will recoup that cost in a short time. For consumers, it's a waste of money.
    Reply
  • ImSpartacus - Thursday, March 10, 2011 - link

    If you only needed the graphics muscle, you should've gotten a Windows laptop.

    Macbooks are for more mobile-minded users. They are thin, strong and have excellent battery life.

    If you just need a solid mobile workstation that isn't going to be moved a lot, Windows laptops are a much better value.
    Reply
  • SimKill - Friday, March 11, 2011 - link

    ODM manufacturers like Clevo and Compal fit your bill perfectly. I got my system in 2009 August and even today I can play most of the games (ofcourse except godforsaken Crysis) at high settings at 1680x1050 (yep, 16:10) It cost me around $1400 but I'm very happy about it so far. Reply
  • SimKill - Friday, March 11, 2011 - link

    Dam, they don't have an edit button. The hardware internals are pretty good with copper heatsinks and heatpipes and what not too... Reply
  • erple2 - Friday, March 11, 2011 - link

    Hrm. Mac's are more of a semi-pro-grade machine. They still lack some of the important pro-grade features of an actual pro-grade machine. Like a Docking Station. Or a spill-resistant keyboard. Or a thumbprint reader. Or a smart card slot. Or a high-gamut monitor.

    While they are well constructed, they still don't have some of the critical features required for a good business laptop - they lack the all important OpenGL performance GPUs for wireframe models (among other things). See some of the high end Elitebooks or Thinkpads (which also cost a bit more than these MacBook Pros).
    Reply
  • tipoo - Thursday, March 10, 2011 - link

    Ah, I just had a dumb, nevermind me. Reply
  • IntelUser2000 - Thursday, March 10, 2011 - link

    http://www.anandtech.com/show/4205/the-macbook-pro...

    "This is a weird one, since the same GPU gave us significantly better performance in the SNB test system."

    Oh gee, I wonder why. The SNB test system used quad core and the Core i5 2410M is a dual core. Quad vs. Dual does have some impact.
    Reply
  • Anand Lal Shimpi - Thursday, March 10, 2011 - link

    It does have some impact, but not in this case. The HD 3000 is actually GPU bound in those tests - not to mention that most games aren't quite so well threaded that 2 v 4 cores should matter.

    Take care,
    Anand
    Reply

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