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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  • anactoraaron - Thursday, April 15, 2010 - link

    Arrandale CULV 13-14" 1440x900 res with discrete ATI 5770mobile + GPU switching.... Imagine having up to 10+ hrs battery life for light internet, word processing work related tasks, being able to watch 2-3 dvd's on battery and then plugging in to game on very high for almost every game! CPU would be 1.3-1.5ghz on battery and "prefer" to run everything single threaded and would run upwards of 2.0ghz "preferring" to be multi-threaded plugged in. That's what I'm waiting for.... the next gen of CULV + Centrino. Can't wait.

    By the way, it's pretty sad that even you Anand are making comments on Apple's prices (since you love Apple the way you do). Guess all relationships that are good eventually become more "Love-Hate"
    Reply
  • l0ts - Thursday, April 15, 2010 - link

    I Wonder what difference can You find between GT330M and GT240M.
    I checked my GT240M in GPU-Z and looks like i got "GT330M "with higher clocks. In six months i'll probably have GT420M. :)
    Thanx NVIDIA!
    Reply
  • Jamahl - Thursday, April 15, 2010 - link

    Who buys this overpriced garbage? Reply
  • TEAMSWITCHER - Thursday, April 15, 2010 - link

    Myself, and a lot of people. I have a late 2006 MacBook Pro that was the first with a Core 2 Duo chip. I have been waiting for the first MacBook pro with a Core i5/i7 processor. This new machine looks exactly like the replacement I have been waiting for. Thank you Anand for the great (and very timely) review. Reply
  • ppayne - Sunday, April 25, 2010 - link

    I buy Macs and am happy to. I run a business and the improved reliability of the Mac means they pay for themselves very quickly. I use my laptop about 8 hours a day (that's on top of my normal work, which I use a Mac Pro for) and any improvement in my workflow is worth a paltry $2000 to my company. If we had PCs at my company I'm sure we'd have a tech guy on payroll who kept things running by now (15 employees). Since I can literally take a hour a month to go around and make sure all updates are run on our Macs instead, there's a pretty clear savings over options we could choose (Windows, "free" Linux etc). Time, convenience, and reliability are actually worth *some* money you know?

    Not everyone is a college student/hobbyist/penny pinching type, although clearly you (and other commenters here) are hating for the sake of hating. For the record, I do PC software development and database work on the Mac and love the irony of not having to keep crap PCs around work to get work done.
    Reply
  • rumimonkey - Thursday, April 15, 2010 - link

    I'm curious for Anand's (or others') thoughts regarding the glossy screens... I'm looking to get my first MBP, and would prefer the 13" (in spite of the C2D). However, I was hoping for a matte option on the smaller model. Is this litmus test really good enough: indoor = glossy, outdoor = matte? I want the 13" because I'd like to be truly mobile, and thus will be beholden to variable lighting conditions. And so if I'm in a public (indoor) place trying to write or read online, what will my experience be? Or if I'm working on the couch at home with the blinds open (hey, I like sunshine), would the gloss drive me bonkers and cause eye strain? Thanks in advance to all who (hopefully) respond with comments and recommendations. Reply
  • kmmatney - Thursday, April 15, 2010 - link

    I have a Dell with the upgraded, glossy screen, and its great in all situations indoors. As long as you can avoid any direct reflections from light sources, a glossy screen is much better indoors, IMO. I've been able to use mine outdoors as well - just need to find some shade. Reply
  • T2k - Thursday, April 15, 2010 - link

    ... and you can answer your question, which one to get. :)

    http://bit.ly/acer750
    Reply
  • quiksilvr - Thursday, April 15, 2010 - link

    Actually, if you get the base 15" model, its $150 extra, because they don't offer 320GB HDD at 7200rpm.

    That is a complete insult. Not only are these things ridiculously overpriced (and their performance isn't even that great for the price either), their upgrades are an insult. Its not like these are magical iPod HDDs. These are the SAME HDDs available on HP and Dell computers. At HP, you can upgrade from a 160GB 5400RPM HDD to a 250 7200RPM HDD for only $30.

    And don't even get me started on their lack of ports. No SD slot on the 17" model? No eSATA? No Blu Ray? Correct me if I'm wrong, but aren't these laptops intended for the PROfessional field?
    Reply
  • ReaM - Friday, April 16, 2010 - link

    I agree with you.

    I have had 10 macs in my life, currently macbook pro and imac.

    This update is ridiculous. The extra cost for the - what now is standard display - is hilarious.

    The only update worth considering is the base 13 inch. But still no i5 nor i3 in it and no display bump up.

    As I wrote, for 1700 buck you can build i7 980X system (hackintosh, if you will) - just as a comparison.

    The current macs are not worth the money.

    Last worthy update was the when unibodies were introduced. But since then, two years went by and nothing changed, except of higher price
    Reply

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