NVIDIA's Scalable Link Interface: The New SLI
by Derek Wilson on June 28, 2004 2:00 PM EST- Posted in
- GPUs
Final Words
In our conversation with NVIDIA, we noted that this technology should work with all software without any modification necessary, and NVIDIA was quoting numbers around 1.87x performance increase over a single card (under 3dmark '03). Of course, this may be an exception rather than the rule, and we do want to run our own tests (as impact will change over graphical complexity). Even more intriguing is the fact that NVIDIA talked about developers being able to take advantage of this technology in their games. It was indicated that, by doing so, games could see a linear (2x) performance increase. If realized, this would be unprecedented in real-world applications of this type of technology.In speaking about why multiple graphics card configurations haven't seen more light in the recent past, NVIDIA mentioned that the PCI bus was the limiting factor in being able to execute something like this on modern hardware. At this point, they still have an unbalanced bandwidth situation due to the x8 bandwidth limit on secondary x16 PCIe slots, but that's nothing like the difference between PCI and AGP (especially as full PCI bus bandwidth can't always be guaranteed to one device).
And then there's the problem of finding motherboards with multiple PCIe slots. The only one that we've seen so far is a multiprocessor board, which hasn't been released yet. To be fair, NVIDIA is targeting the system builders first, and won't be pushing a consumer SLI upgrade package until later (possibly this fall). The success or failure of this product will likely not rest on its technical merits, but rather on the availability of suitable motherboards, and the cost of the upgrade. We can see some hardcore gamers out there spending $500 on a card. We could see some even going so far as to upgrade their entire PC if it meant better performance. But it is hard for us to see very many people justifying spending $1000 on two NV45 based cards even for 2x the performance of one very fast GPU; perhaps if NVIDIA cripples some of its GPUs to work only as slaves and sells them for a (very) reduced price as an upgrade option. Even then, this isn't going to have as easy a time in the marketplace as the original 3dfx SLI solutions.
Now, what would really work in NVIDIA's favor is if they engineer their NV5x GPUs with backwards compatible SLI technology. Even the promise of such a thing might be enough to get some people to pick up an NV45 with the knowledge that their future upgrade would actually be an upgrade. For those who upgrade every generation, there would be a way to get more power for "free", and those who wait 2 or more generations to upgrade might have a new reason to take the plunge. This scenario is probably wishful thinking, but we can dream, can't we?
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Wonga - Monday, June 28, 2004 - link
Hey hadders, I was thinking the same thing. Surely if these cards need such fancy cooling, they need a little bit of room to actually get some air to that cooling??? And to think I used to get worried putting a PCI card next to a Voodoo Banshee...DigitalDivine - Monday, June 28, 2004 - link
does anyone have any info if nvidia will be doing this for low end cards as well?klah - Monday, June 28, 2004 - link
"But it is hard for us to see very many people justifying spending $1000 on two NV45 based cards even for 2x the performance of one very fast GPU"Probably the same number of people who spend $3k-$7k on systems from Alienware, FalconNW, etc.
Alienware alone sells ~30,000 units/yr.
http://money.cnn.com/2004/03/18/commentary/game_ov...
hadders - Monday, June 28, 2004 - link
Whoops. duh. Admittedly all that hot air is been exited via the cooling vent at the back, but still my original thought was overall ambient temperature. I guess there would be no reason why they couldn't put that second PCIe slot further down the boards.hadders - Monday, June 28, 2004 - link
Hmmm, to be honest I hope they would intend to widen the gap between video cards. I wouldn't think the air flow particularily good on the "second" card if it's pushed up hard against the other? And where is all that hot air been blown?DerekWilson - Monday, June 28, 2004 - link
The thing about NVIDIA SLI is that the technology is part of die ... Its on 6800UE, 6800U, 6800GT, and 6800 non-ultra ... It is poossible that they disable the technology on lower clocked versions just like one of the quad pipes is disabled on the 12 pipe 6800 ...The bottom line is that it wouldn't be any easier or harder for NVIDIA to impiliment this technology for lesser GPUs based on the NV40 core. Its a question of will they. It seems at this point that they aren't plannig on it, but demand can always influence a company's decisions.
At the same time, I wouldn't recommend holding your breath :-)
ET - Monday, June 28, 2004 - link
Even with current games you can easily make yourself GPU limited by running 8x AA at high resolutions (or even less, but wouldn't you want the highest AA and resolution, if you could get them). Future games will be much more demanding.What I'm really interested in is whether this will be available only at the high end, or at the mid-range, too. Buying two mid-range cards for a better-than-single-high-end result could be a nice option.
Operandi - Monday, June 28, 2004 - link
Cool idea, but aren't these high end cards CPU limited by themselves let alone paired together.DerekWilson - Monday, June 28, 2004 - link
I really would like some bandwidth info, and I would have mentioned it if they had offered.That second "bare bones" PCB you are talking about is kind of what I meant when I was speaking of a dedicated slave card. Currently NVIDIA has given us no indication that this is the direction they are heading in.
KillaKilla - Monday, June 28, 2004 - link
Did they give any info as to the bandwidth between cards?Or perhaps even to the viability of dual core cards? (say having a sandard card, and adding a seperate PCB with just the bare minimum, say GPU, RAM and and interface? Figuring that this would cut a bit of the cost off of manufacturing an entirely seperate card.