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New MacBook Pros have dual-GPU, no SLI
Author: Gareth HalfacreePublished: 17th October 2008
Although the new MacBook Pros have two GPUs, chaining the two together via SLI won't be a possibility.
According to the guys over on MacRumours, although the new MacBook Pro units feature both an on-board Nvidia GeForce 9400M GPU for low-power graphics processing on the go and a beefier GeForce 9600M GT discrete card for better performance when hooked to the mains, there's no possibility of combining the two in a hybrid SLI rig.
Instead of the performance-boosting GeForce Boost functionality many were expecting from this latest top-end laptop, the two chips are used purely for energy saving purposes – dubbed HybridPower by Nvidia. While anything that gives a boost to a laptop's battery life is welcome, it is somewhat galling to know that at any given time there is a chunk of GPU horsepower that is sat inside your exquisitely designed hunk of metal doing absolutely nothing.
The lack of GeForce Boost is described by MacRumours as a “hardware limitation” of Apple's current design, which means it's unlikely we'll be seeing a MacBook Pro capable of dual-GPU graphics performance until the next hardware refresh cycle. Rather embarrassingly, the site has also revealed that the process of switching between high-power discrete graphics and energy-saving integrated graphics requires that the user logs out of MacOS X – which makes moving between battery and mains power during a single session rather less convenient than you might expect.
Any Mac fans out there hoping for more from this latest revision, or is the inability to chain the two GPUs together for ultra graphics grunt a minor issue? Share your thoughts over in the forums.
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Doesn't bother me, i've tried SLI in my PC in the past and with two indentical cards its hard enough to get games to scale to a worthwhile increase/wattage - im guessing there is even less support for SLI in OSX :)
Just another couple of reasons not to buy one, sat next to 'inordinate waste of money' and 'bank balance on life support'.
make a really fully functioning product not a chopped down piece of crap and charge an extra £500 of it
rant over
I also believe it's a bit of forward thinking on Apples part with OpenCL and Grandcentral on the horizon in 10.6, when the redundant GPU will be used as a CPU when needed.
As login/log out to swap, it takes 7 seconds, and fwiw, most users will stick with the discreet instead of swapping between them. As I've said, the 9400 is an inheritance due to it being the main chipset controller too.
Finally, it's purley a software limitation atm with utilizing both GPU's, which does mean it will be addressed at a later date either by Apple, NV or some 3rd party dev.
Apple see themselves as champions of style and designers*, when do those two things need SLI? Never. Want SLI on a Mac? Buy a Mac Pro, install Windows, and use two single 6-pin power cards which don't need the mobo based bridge. Other than that, simply not going to happen.
*Apples Mission Statement: Apple ignited the personal computer revolution in the 1970s with the Apple II and reinvented the personal computer in the 1980s with the Macintosh. Today, Apple continues to lead the industry in innovation with its award-winning desktop and notebook computers, OS X operating system, and iLife and professional applications. Apple is also spearheading the digital music revolution with its iPod portable music players and iTunes online music store.
Sure, it will be addressed by Apple in their next hardware refresh and they'll charge you half again the price of the notebook now for what amounts to a driver update.
Also, logging out and then back in may take 7 seconds simply for that act, but then consider the time it would take you to wsave all of your current work and then reopen and load all of your data again once you've logged in again. We're talking more like a 30s-1min waste of time that could have been avoided completely if NVIDIA was half as good at writing software as people give them credit for.
+1 to that, Apple couldnt care less about gaming really. Its all about GPGPU, im hoping a further itteration of Aperture gets that treatment, never was a fan of PS and Lightroom. It would really give the Final Cut guys a hand.
+1 on the option to use a low power GPU as well. SLI use would be near pointless, you shouldnt be gaming on a mac anyway, they just arnt designed for it. Its probably a case of they wanted the higher power one, then lumped in a low power one too to keep battery life reasonable.
well, with GT200 series so successful at saving power, why can't they have nVidia make a GT200 based laptop chip for them? that'd push up performance and saves power when needed
If you're using a heavy GPGPU program (CS4, for example), and you're sitting on an AC adaptor, why should the shaders sitting on the IGP be sitting there idle? Hybrid SLI would enable the system to switch on (and off) the extra power of the IGP (Or of the discrete chip) as and when. Sitting at the desktop? IGP only. In CS4 and doing nothing? IGP only. In CS4, processing an image? Switch on the discrete for as long as the processing takes, then switch it back off again. Drop it in and out of use/power as and when it's needed, rather than having an "most-but-not-all or least" approach.
TBH, I think Hybrid SLI is a great starting point, but imagine it extended out. 120 banks of 4 shader cores, all independently powerable. So, sitting at desktop, all the banks are off. Moving windows around under vista? one bank powered, the rest off. Loading Crysis? One bank on, the rest off, ready to power up within a single frame. Playing Crysis? Power on as many banks as are needed to render the current frame, and powering on more if the estimated load for the next frame is greater.
Like the modern V8 engines do. If you're not standing on the gas pedal, 4 of the cylinders aren't getting any fuel or spark. Same thing here, scaled up.
At least, that's how I'd like to see it done.
"GeForce boost" is NOT a given if the two cards are heavily asymmetric. In current SLI implementations, two cards render alternate lines, thus rendering speed is twice that of the slowest GPU. This is how Nvidia implements is, not Apple. In the future Nvidia (or other GPU manufacturers) may split this into 2 lines to 1 or 3 to 1 or whatever, but currently, enabling SLI if the speed differential is large than two would be detrimental to rendering speed.
Now, since the 9600 GT has twice the pipelines of the 9400M, the latter being, furthermore, an integrated chip with shared memory, it is clear that he first is twice as fast than the latter. Therefore, with Nvidia's current implementation of SLI (NOT because of apple), SLI with this configuration would be in fact SLOWER than using just the 9600 GT.
You can have SLI with the integrated 9400M and, say, a 9300 GT or a 9500 GT. But this would be slower than or comparable to the 9600 alone.
This does NOT mean that the second GPU cannot be used in a future version of the OS (for example to do other computations), just not in a SLI version.
Therefore, instead of blasting Apple, document yourself - be informed. I am pissed off, as well, because of the exclusion of FW from the MacBook -- which means, if I upgrade my wife's laptop, it has to be an MBP -- and I will have to use a FW800 to FW400 adapter on my next MBP. But, frankly, there is nothing wrong with the graphics on the MBP.
Roberto