Hybdrid SLI on MBPs 9400M+9600M GT

[P40L0]

Hi, I'm Paolo, and I'm Italian, so sorry for my bad english...

I'm going to buy a brand new Macbook Pro 15" 2.8Ghz with integrated NVIDIA 9400M chip + the discrete NVIDIA 9600M GT graphic cards for my University Career and I'm reading on the web that there's already a feature (on Leopard) that switches in real-time the GPUs in order to save battery life without logging off choosing one single chip at time like before, but there's no SLI function yet.

I was wondering if and when an Hybrid-SLI technology will be available both for Leopard and Windows (for gaming). I'm going to install Snow Leopard and create a second partition of Windows 7 x64 via Bootcamp only for Gaming (Crysis, Far Cry 2, The Orange Box and others) and it will be awesome to enable some sort of SLI, with both of GPUs working togheter, increasing framerates and visual quality!

So, there's some news or update about that? It's just a matter of time and software or the hardware is not capable yet?

Thanks very much!

 

[J the Ninja]

It will never happen. Why? Because it will actually result in slightly worse performance, due to the downclocking and core shutdowns the 9600 would be forced to undergo to be paired with the 9400. I don't feel like typing up a long explanation of why, as I've already done so on this site several times, as have other people. You can search for those or read through Nvidia's documentation if you are curious as to the gritty details.

 

[P40L0]

It will never happen. Why? Because it will actually result in slightly worse performance, due to the downclocking and core shutdowns the 9600 would be forced to undergo to be paired with the 9400. I don't feel like typing up a long explanation of why, as I've already done so on this site several times, as have other people. You can search for those or read through Nvidia's documentation if you are curious as to the gritty details.

Are you sure about that?
I've just found this: https://www.macrumors.com/2008/10/22/macbook-pros-nvidia-chipsets-can-support-dual-gpu-and-8gb-ram/ , and here it seems it's only a matter of time...

 

[J the Ninja]

Fine, I'll type it again.

Two GPUs in SLI must be IDENTICAL. Same numbers of cores, same clocks, same everything. If they are not, the faster one will begin disabling hardware units and underclocking itself to match the slower chip. Let's compare really quick:

9400M
Number of stream processors: 16
Core clock: 450Mhz
Stream clock: 1.1Ghz


9600M GT
Number of stream procs: 32
Core clock: 500Mhz
Stream Clock: 1.25Ghz


Now, let's look at when we'd end up with combining them:

Number of stream procs: 32
Core clock: 450Mhz
Stream Clock: 1.1Ghz

Oops. We now have essentially the same amount of hardware units as the 9600 by itself, expect they're now clocked lower, and instead of all being on one die and all having discrete GDDR3 RAM, now only half of them have the discrete, fast memory, and the other half are on a completely different chip separated by a PCIe x16 link.

Finally, if you look at this page, you'll notice that GeForce boost (combining discrete and integrated GPUs) isn't supported on the 9600M, or anything that isn't comparably weak to a integrated GPU, for that matter. http://www.nvidia.com/object/hybridsli_notebook.html

tl;dr version: It will not ever happen. It is not supported in the hardware, period. And it is not supported because doing it in the first place is silly.

 

[P40L0]

I see.
Well, I really hope they will workaround this, maybe creating something software/driver-level to use "different" GPUS, clocks and chips instead of classic NVIDIA SLI, something like Ati does or something like Hybrid Power, but for Geforce Boost.

I saw a section inside the nvidia site that show a "Coming Soon" to Hybrid SLI on Notebooks, Apple included, so, let's hope something at least...

Meanwhile, I hope that a single 9600M GT with 512MB of ram will run in a good/playable way Crysis on Windows 7 x64 fully updated.

Thanks for the answer!

 

[Tallest Skil]

Why? Forget this. There is just no real point to it.

 

[P40L0]

Why? Forget this. There is just no real point to it.

Dramatic increase of performance anyone?

 

[J the Ninja]

Dramatic increase of performance anyone?

*facepalm*

THERE IS NO PERFORMANCE INCREASE! NOT NOW, OR EVER!

SLI DOES NOT WORK THAT WAY!


Edit: Crossfire doesn't work that way either, before you suggest a second time that ATI has some magic sauce for this.

 

[BlackNinja360]

It will never happen. Why? Because it will actually result in slightly worse performance, due to the downclocking and core shutdowns the 9600 would be forced to undergo to be paired with the 9400. I don't feel like typing up a long explanation of why, as I've already done so on this site several times, as have other people. You can search for those or read through Nvidia's documentation if you are curious as to the gritty details.

SLI proper yes, that would require two identical GPUs, not the case with Hybrid SLI which require 1 integrated GPU in ex: Nvidia 9400M and 1 dedicated GPU like the 9600m GT for instance. When combined both GPUs using the technology would provide significant performance increase especially for 3d games. The question is not hardware as the Macbook Pro could easily do this like most PC notebooks can, but software on Apple's part. They would simply need to allow a software update to unlock this feature. In addition if this feature were to be enabled it would be unclear if it would even work under Windows as currently the Hybrid power technology, which allows users to switch between the two GPUs is unavailable under Windows. In windows you may only use the 9600m GT. One final note; Apple may have intentionally done this due to the Macbook Pro's form factor, while most PC bulky as the may be have well designed cooling systems, most Mac notebooks are designed very thinly which adversly affects more powerful gpus due to insufficient cooling technology.

 

[oregon2]

I don't think anyone has mentioned it, but PhysX (same as hybrid sli?) could definitely run on the 9400. PhysX does NOT require the cards to be matched, and can really only make games look better.

 

[bombjack]

Just as someone mentioned, there would probably be cooling problems using both GPU's at the same time. I have a 6 months old MBP 2.8 unibody which has been in for repair 3 times, i.e. change of logic board, due to overheating problems when gaming with 9600 GT GPU activated. The problem is still not solved. See http://discussions.apple.com/thread.jspa?threadID=1882489 (As far as I know, Apple has not even officially admitted there is a problem).

For me, the problem persists even after three logic board changes. With current bard I only had "Black screen of death" twice, and I probably should let them change again, but I have given up on getting this solved.

 

[P40L0]

SLI proper yes, that would require two identical GPUs, not the case with Hybrid SLI which require 1 integrated GPU in ex: Nvidia 9400M and 1 dedicated GPU like the 9600m GT for instance. When combined both GPUs using the technology would provide significant performance increase especially for 3d games. The question is not hardware as the Macbook Pro could easily do this like most PC notebooks can, but software on Apple's part. They would simply need to allow a software update to unlock this feature. In addition if this feature were to be enabled it would be unclear if it would even work under Windows as currently the Hybrid power technology, which allows users to switch between the two GPUs is unavailable under Windows. In windows you may only use the 9600m GT. One final note; Apple may have intentionally done this due to the Macbook Pro's form factor, while most PC bulky as the may be have well designed cooling systems, most Mac notebooks are designed very thinly which adversly affects more powerful gpus due to insufficient cooling technology.

Like I tough...

The feature it's possible indeed when:

-It will be released an OS and Driver update (both for OSX and Windows)

and/or

-It will be "fixed" the cooling problem: via software or hardware (<-more possible the last, so: new models or regenerated old one)

Let's continue to hope hearing something soon with Snow Leopard out in stores...