Apple's GPU Switching Technology

The Core i5 and i7 CPUs all come with their own on-package CPU called Intel's HD Graphics. This DX10-class GPU is capable of playing games and has a capable HD video decode engine, but it's no match for a discrete GPU.

As I mentioned earlier, all of the 15 and 17-inch MacBook Pro models ship with NVIDIA GeForce GT 330M discrete GPUs in addition to the two Intel chips (Core i5 + H55M). Despite being built on a 40nm process, the GT 330M could easily knock off an hour of battery life just by sitting idle while you type away in Pages.

Apple has had this problem before. The previous unibody MacBook Pros with discrete graphics had a software switch that you could use to turn the discrete GPU on/off. It was a pain to use however since you had to log out after switching modes.


The Old Method

With the new MacBook Pro, Apple implements an automated switching system similar to NVIDIA's Optimus technology. Instead of relying on application profiles, OS X looks at the functions called by any running application and determines whether the Intel HD Graphics is sufficient or the GeForce GT 330M is needed. Applications like video playback are low key enough to run exclusively on the Intel HD Graphics, while 3D games and applications that take advantage of GPU acceleration appear to wake up the GT 330M.

Update: Apple has given us a list of frameworks that will trigger the discrete GPU, they primarily include: OpenGL, OpenCL, Quartz Composer, Core Animation and Core Graphics. Also, if you plug in an external display the discrete GPU is also turned on.

Apple has also confirmed that both the discrete and integrated graphics cores have their own connection to the display. There's no copying of frame buffer data, the GPU that's in use is the one that's storing and displaying the screen. If the integrated graphics core isn't in use it is put into its lowest power state.  If the discrete GPU isn't in use it's completely shut off.

Power Consumption Comparison
  Intel HD Graphics Only GeForce GT 330M
Idle at OS X Desktop 11.5W 15.1W

The switching process is seamless and there's no indication of what GPU is being used at any given moment. That's both good and bad. You don't have to muck with any software switches, but you also rely on Apple to make the right decision based on your current workload. Without a way of telling what is making the discrete GPU wake up, there's no way to know whether something as simple as leaving an application open is causing you to have lower-than-ideal battery life.

There's also no way to turn the GeForce GT 330M off completely, regardless of application. This is one area where Apple completely wrestles control away from the end user. I'm all for automated switching systems, just not ones that don't reassure me that they're always making the right decision.

Despite using a NVIDIA GPU, there's no support for Optimus under Windows 7 on the new MacBook Pro. The GeForce GT 330M is always in use there regardless of whether you use an Optimus enabled driver or the 196.21 driver that comes with the MacBook Pro.

No AES-NI Support in OS X? The GeForce GT 330M
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  • Rod Hagen - Thursday, April 15, 2010 - link

    It is much, much easier on all of the unibody models than on the pre-unibody ones from before October 2008 (assuming this is what you had previous experience of) .

    Pretty much a five to ten minute job at worst in terms of the hardware side of things.

    Cheers

    Rod
    Reply
  • MadMan007 - Thursday, April 15, 2010 - link

    So I read this and I thought 'OK, Anand is impressed with the battery life' so I figured 'Hey why not see how it compares to other laptops?' I had to go to other articles because this review only has Macs - fair enough for the Mac fanbois who won't consider anything else anyway but not for those who might be open-minded. But what did I find? Sadly Windows laptops run an entirely set of battery test suites. 'Completely idle' 'Flash web browsing' (I think the Macs get a big boost by having non-Flash browsing and that seems like a big fudge to me) and then '720p video playback.'

    To my surprise, looking at results, the Macbook batery life is NOT super overwhelmingly impressive. Most of the other laptops that have high(er) battery life have CULV CPUs, fair enough they aren't as fast as the MacBook but then they will run any of the 'battery test' suites just as well. The recent Lenovo is however a Core i5 and gets good battery life.

    So Anand, please stop the shenanigans with Apple battery life hype and use tests that are actually the same (as much as possible -Safair might not be available on Windows for example) across platforms.
    Reply
  • Anand Lal Shimpi - Thursday, April 15, 2010 - link

    I addressed the Windows comparison in some earlier articles, the most recent of which is here:

    http://www.anandtech.com/show/2870/done-for-2009-t...

    You'll also note that Jarred runs an idle battery test in all of our Windows reviews, that's the most comparable to the light web browsing test. Some of the recent entries we've tested have gotten a lot better but take the Lenovo ThinkPad T410 for example:

    http://www.anandtech.com/show/2976/lenovo-thinkpad...

    With a 94Whr battery it delivers less battery life idle at the Windows desktop than this 77.5Whr 15-inch MBP while running our light web browsing test.

    The gap is closing but it's still there. The first link shows that the gap only really exists in light load scenarios where there's lots of idle time (e.g. reading, web browsing, writing).

    Take care,
    Anand
    Reply
  • maler23 - Thursday, April 15, 2010 - link

    @MadMan007

    Hey dude, show a little respect. I can understand wanting a little perspective but maybe rephrase your request...unless it's a rant, in which case, flame on, sir :)

    How about this:

    =============

    Anand, once you get all three models tested, could you include some comparison battery tests that include Flash as it that is a reality for most webpages(including the comment page I'm typing out right now). In addition, I would love to see a display comparison. I often see this site grumbling about contrast and color range and such with other laptops(recent Asus models, for example) but I would love to see Macbooks thrown into the bunch for comparison.

    =============

    cheers!

    -J
    Reply
  • Anand Lal Shimpi - Thursday, April 15, 2010 - link

    I should also add that I do have a video playback and flash web browsing test for the MBP, they simply didn't make the final cut for yesterday's review due to time constraints however I'll be adding in the data in the next day or so :)

    Take care,
    Anand
    Reply
  • sky7i - Thursday, April 15, 2010 - link

    Hmm, I was all set to get one but now I'm worried about heat and noise issues. I absolutely detest sweaty palms and am very sensitive to machine noise, often preferring my Acer netbook to the Mac as the Acer is silent.

    My current machine is an original Core Duo 15" MacBook Pro. It also has two fans (one a bit wobbly) but temperature wise it's fine. Will the new 15" be warmer?

    I was also contemplating the SSD 128gb option for an extra $280, for the silence and performance. Will this help it run cooler? Is there a better option in that price range? The Intel SSD seems wonderful but it's $500. Maybe I'll just try to find a single-platter 250gb drive instead.

    Thanks for any input.
    Reply
  • solarisking - Thursday, April 15, 2010 - link

    I have a late 2006 MBP and every since I had a warranty claim on the power brick (it stopped lighting orange/green/off correctly) they sent me a new one which was smaller. I think I figured out over time that it *seemed* like the new brick charged my MBP slower than the old one. Without the old brick I was unable to confirm. As it stands now, it can take up to 4 hours to charge the damn battery, if not longer. And I have two batteries! So hopefully, the new brick has more DC current and charges more quickly. Given a larger battery capacity that's my guess, and warmer laps are the result. And BTW, my MBP can get pretty dang hot when being recharged. Reply
  • laela - Thursday, April 15, 2010 - link

    How is the battery life under Windows 7? Thanks for a great review! Reply
  • mikeev - Thursday, April 15, 2010 - link

    I too would like to know this. I am extremely curious as to how bad the Windows 7 battery life is with that GPU cranking away the whole time, since I play a lot of games.

    Also, do you have any guess as to if NVIDIA or some 3rd party (a passionate user?) might possibly create a Windows driver/utility that will allow switching between the IGP and GPU like in OSX?
    Reply
  • jasperjones - Thursday, April 15, 2010 - link

    I think it's completely reasonable that Anand doesn't provide results for battery life under Win 7. iyam, if you don't use OS X as your primary OS, you shouldn't get a Mac. It's as simple as that. Reply

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