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


View All Comments

  • oldbriones - Thursday, April 15, 2010 - link

    I am disappointed, once again, that apple slapped on crappy TN panels to their MacBook Pro.
    Use of IPS panels in iPad, new iMacs, and new Cinema Displays were welcome changes for the better
    (far superior viewing angle, color integrity). Why not in the Pro line of MacBook ?!
  • beginner99 - Thursday, April 15, 2010 - link

    to increase margins. fanboys will buy it anyway (no sane person would for this price...)
    It's like 800$ extra compared to similar dell, hp,... models.
  • that_guy_mike - Thursday, April 15, 2010 - link

    by that logic no one would drive a mercedes or bmw either since you can get a honda for way less, and they're clearly the same since they are all just cars. Reply
  • The0ne - Thursday, April 15, 2010 - link

    That's retarded. When referring to laptop the margins/difference in hardware and much less than comparing vehicles. It's the same hard drive, same memory, etc. A car may be a car but the process of getting there is absolutely different, less being the same part.

    Now if you were to say, why not buy a car with almost the same parts and materials, slap on a Mercedes logo, and charge a premium for it then that would make more sense.
  • mikesmithson - Friday, April 16, 2010 - link

    You mean how like the difference between a Honda Accord and an Accura TL? Like how they use a lot of the same parts... Accord starts at $21,000; TL at $35,000... Reply
  • maler23 - Thursday, April 15, 2010 - link

    Prolly the odd man out, but I'm waiting for a review of the 13 inch model. I was already pretty much decided on the MBP 13in anyways, so any upgrades for the same price is a perk.

    The lack of Arrandale kinda hurts though; I'm also wondering if the nVidia 320M makes things run any hotter. I'd love to hear a good reason why Apple skipped the Core i3 and stuck with the Core Duo. I'm assuming it was a space concern due to the whole Intel/NVidia chip kerfuffle and they wanted to keep the same sized chassis?

    Anand, any bets on an Arrandale update for the Fall for the MBP 13?


  • solofest - Thursday, April 15, 2010 - link

    I second the request for a 13" review. I'd like to see how the 320M stacks up, as well as some real world battery tests. Re: an Arrandale update for the 13" in the fall, sounds like Apple may as well wait until Sandy Bridge? Reply
  • solipsism - Thursday, April 15, 2010 - link


    The tests of Core-i3 and having to use Intel HD over a speed bump in C2D and Nvidia 320M tell me that Apple made the right choice. I can't see the 13" MBP maintaining the same price point or increasing the battery duration with a discrete GPU.

    I think Anand is correct in that the a Fall release is inevitable. While this is is a decent update I think it is meant to be a stopgap for more radical changes. What should have come about 7-8 months later may jut 4-6 months later due to the Arrandale supply issue.

    For the next release, the 13" MBP may have to drop the ODD to make room for the component and cooling, and to lessen the blow of the GPU cost. Apple obviously isn't going to offer Blu-ray so I'd say they are just holding onto the internal ODD until offering Mac OS X Restore Discs on a 16GB SD Card is more viable. I don't think they added SD to the 13" and 15" so many years after it was standard, just to say "me too". I think it'll be the new way to restore the disc. It's how I've been doing it for a couple years.

    PS: I wish Anand would have mentioned the other aspects of this revision: audio over DisplayPort or HDMI, and force accelerated scrolling.

    PPS: I don't recall seeing any mention of how Nvidia Optimus doesn't power down the IGP when the GPU is active. I'd like to see the power usage differences between Windows and Mac OS X on these machines now that Apple has graphics switching in place. It's too bad Optimus won't work under BootCamp.
  • DLeRium - Thursday, April 15, 2010 - link

    How easy is it to replace HDs in the new unibody MBPs? I have a 2008 MBP (15") and it takes a great amount of work to disassemble just to change out a hard drive. With HD prices so cheap, it's not too hard to buy a 500gb 7200 RPM drive and stuff it in. However, I'm often discouraged when it takes a lot of tampering. I've disassembled my Wii to mod chip it. I've disassembled camera lenses to blow out dust behind the front element, but I'm not the most hands on guy and I hate repacking things together. I often mess up there. Reply
  • solipsism - Thursday, April 15, 2010 - link

    It's pretty simple. Check iFixit for the 2009 MBPs. You basically take the entire bottom off, about 10 screws, and then a 1-3 screws for the HDD. It'll takes you an extra 2 minutes over the previous models with the latch and door exposing the HDD and battery. Reply

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