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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  • mckirkus - Thursday, April 15, 2010 - link

    I have a feeling a lot of the people that use these make movies which requires bulk storage. Even a 256GB SSD would tack on at least $500 Reply
  • Pneumothorax - Thursday, April 15, 2010 - link

    As being one of those poor saps that "upgraded" to the previous gen MBP and realized I can only run my Intel 160gb G2 reliably at SATA I speeds, this new laptop makes me wary of going for another round of disappointment... So is it fixed? Reply
  • webdev511 - Thursday, April 15, 2010 - link

    Envy 15 has
    a better GPU ATI 5830
    better top end CPU i7 820m
    higher ram capacity 16GB
    7200 RPM drives standard Dual SSD available

    I had high hopes for this rev of MBP, but suffice to say, I'm unimpressed.
    Reply
  • flyguyjake - Friday, April 16, 2010 - link

    1) Is the display refresh rate 60hz, or 120hz?

    2) What is the contrast/dynamic contrast ratio?

    I phoned Apple today 3x and couldn't get the answers from them. I did however get the following information.

    I'm told that if I install boot camp / Win 7 w/USB Blu-Ray drive I can get 1080P on the LCD panel. BUT what's even more exciting is that the MiniDisplay port, via HDMI Griffin adapter, will fully support 1080P video & DTS-HD, TrueHD audio bistream. The i7-620M has PVAP 1.5 (protected video audio path) which is needed for the HD audio & the 330M is HDCP compliant.

    What is even MORE exciting is the possibility of 3D !!! The Geforce 330M supports Nvidia 3D vision.

    Can this setup play Blu-Ray 3D?

    Can this all really be true?
    Reply
  • prof.yustaz - Friday, April 16, 2010 - link

    Anand Lal Shimpi,

    "The day has finally come. For nearly a year now I’ve been telling everyone who wanted a new MacBook Pro to wait for Arrandale."

    Right. But at the end of the review you also said this: "With a Core i5 and GeForce GT 330M, the new MacBook Pro can get uncomfortably warm under use. I found that the previous generation unibody ran cooler. Intel expects to see Arrandale power consumption go down sometime after the middle of the year with a future rev of the processor. I'm guessing that's what'll be used in the inevitable Fall update to the new MacBook Pro lineup."

    Are you saying that Apple will do another refresh in about 5 months just because Intel will release another rev of the CPU? And if that happens, do you expect to see a meaningful reduction of heat and perhaps an even better battery performance? In other words, is it really worth the wait?

    "You're paying for the design, build quality and ultimately the right to use OS X. If those things don't matter to you (particularly the OS X item) then you'd be much better off with an ASUS or Dell."

    Those things do matter to me, a lot, minus the OS X. But I do not see being much better off with an ASUS or Dell precisely because those things matter to me. Grinding my teeth, I would be willing to sacrifice Apple's design and build quality for function, but ASUS, Dell, HP or Sony do not offer the same battery life and screen resolution as Apple's 15 inch laptop. Am I missing something here? And isn't it true that somewhat comparables offerings from Dell and HP, for example, run even hotter than the most recent Apple's 15 inch laptop?

    "If you're curious about what's next, I have two words for you: Sandy Bridge. Due out sometime in Q1 2011, Sandy Bridge looks incredible based on early performance data. No word on when we'll see it in notebooks but if you like torturing yourself, waiting for Sandy Bridge will pay off."

    I need a laptop, but I do not have to have it right now. Plus, I do not want to pay over $2,000 for a laptop now if it is going to be blown away in a year or so. Could you please elaborate a little on what can we expect to see in terms of design and function assuming Apple implements Sandy Bridge in a future rev of MBPs? Will they be thinner? Will they have a significantly better battery life and run a lot cooler?

    P.S. Also, if you were to purchase the current 15 inch MBP, which combination of the CPU, Memory and HD would you choose to stay below $3,000 (closer to $2,500).

    Thank you.
    Reply
  • lparsons - Sunday, June 20, 2010 - link

    "ASUS, Dell, HP or Sony do not offer the same battery life and screen resolution as Apple's 15 inch laptop."

    I have to agree with you here. I've been looking around a lot, and while the MBP is expensive, Apple has put together an excellent set of components. They make good choices wrt battery life and performance tradeoffs. The closest thing I can find is the Thinkpad T510 which is a very solid machine, but lacking in 3D graphics performance and I'm not keen on the 16:9 screen. It doesn't have quite the same build quality (though it's still very good) and the batter life isn't quite as good, in part due to the lack of switchable graphics.

    I'm hoping to keep the machine for while, so the i7 seems to make sense. Annoyed that the 4GB is 2x2GB, making a future upgrade more expensive than necessary, so I'm debating the 8GB. Would also love an SSD, but I'm thinking that I'll upgrade to that later when the price (hopefully) drops, since I could really use the capacity of the 500GB drive and the Apple SSDs are extremely expensive. Also, the Hi-Res screen is a must for me.
    Reply
  • ihouman - Friday, April 16, 2010 - link

    Anand, I read this article yesterday and your conclusion between the i5 and i7 were slightly different, as were a few other points. If you had a change of heart, you should append the changes to the end as opposed to removing your original opinion. It creates the image that 'someone' helped persuade your new opinion. Reply
  • Anand Lal Shimpi - Friday, April 16, 2010 - link

    Since the original publication I got my hands on a Core i7 based 15-inch model. While I expected the clock speed/cache increase to only result in a less-than-10% performance increase, it ended up doing more than that. It's based on this data (and only this data) that I updated the conclusion, I will edit the conclusion to reflect that this change was made however :)

    Take care,
    Anand
    Reply
  • Apolloe - Friday, April 16, 2010 - link

    Am I right in assuming that your Left 4 Dead and World of Warcraft tests were done with the i5 15", and not the i7? I assumed this since your info on the GPU there had 256MB, while the i7 MBP has 512MB.

    If so, any chance of showing the fps results from these games? If not, an answer to the above would be suffice :)
    Reply
  • cyrexo - Friday, April 16, 2010 - link

    Thanks for the nice review. Could you please measure the battery life with the i7 also?

    the heat difference between i7 and i5 would also be a nice information which could help me with my decision^
    Reply

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