NVIDIA's Scalable Link Interface: The New SLI
by Derek Wilson on June 28, 2004 2:00 PM EST- Posted in
- GPUs
Introduction
The major trend in computing as of late has been toward parallelism. We are seeing Hyperthreading and the promise of dual core CPUs on the main stage, and supporting technologies like NCQ that will optimize the landscape for multitasking environments. Even multi-monitor support has caught on everywhere from the home to the office.One of the major difficulties with this is that most user space applications (especially business applications like word processors and such) are not inherently parallel. Sure, we can throw in things like check-as-you-type spelling and grammar, and we can make the OS do more and more things in the background, but the number of things going at once is still relatively small.
Performance in this type of situation is dominated by the single threaded (non-parallel) case: how fast the system can accomplish the next task that the user has issued. Expanding parallelism in this type of computing environment largely contributes to smoothness, and the perception that the system is highly responsive to the user.
But since the beginning of the PC, and for the foreseeable future, there is an aspect of computing that benefits almost linearly with parallelism: 3D graphics.
NVIDIA 6800 Ultras connected in parallel.
For an average 3D scene in a game, there will be a bunch of objects on the screen, all which need to be translated, rotated, or scaled as per the requirements for the next frame of animation of the game. These objects have anywhere from just a few to thousands of triangles that make them up. For every triangle that we can't eliminate (clip) as unseen, we have to project it onto the screen (from back to front objects which are further from the viewer are covered by closer ones).
What really puts it into perspective (pardon the pun) is resolution. At 1600x1200, 1,920,000 pixels need to be drawn to the screen. And we haven't even mentioned texture mapping or vertex and pixel shader programs. And all that stuff needs to happen in less than 1/60th of a second to satisfy most discriminating gamers. In this case, performance is dominated by how many things can get done at one time rather than how fast one thing can be done.
And if you can't pack any more parallelism onto single bit of silicon, what better way to garner more power (and better performance) than by strapping two cards together?
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Falloutboy525 - Tuesday, June 29, 2004 - link
acutally I wouldn't be surprised if one of the board manufactures puts 2 cores on one card. but man just thinking aboutt he physical size of the card gives me nightmares.Pumpkinierre - Tuesday, June 29, 2004 - link
The last of the SLI Voodoo2s had a dual gpu on a single board for one PCI slot. I cant see why the same couldnt be done for a dual 6800 gpu board on a single x16 PCIe slot which is nowhere near saturation with current gpus. Load balancing would be accomplished on board. In fact, they could do it on AGP 8x as well. They could extend this to multiple gpu (also possible on a 3x 16PCIe slot mobo (+ 3slot bridge) if it ever came out. Just think of the cooling with a Prescott cpu thrown in! Put a Vapochill to room temperature!Backward daisy chaining of components is a great idea but I doubt whether the greed of manufacturers will let it happen. The concept should not be limited to gpus but extend to mobo/cpus as well. A high speed link bus(Hypertransport perhaps, but not I2B) should allow systems to act as multiple processor system albeit with a little added latency. With parallel processing and multithreads around the corner, it would be useful to those who detest the enormous waste in the IT industry.
quanta - Tuesday, June 29, 2004 - link
Actually, NFactor, GeForce 6800's dedicated video codec is a step behind from ATI's videoshader. It adds transistor counts for things that can already be done by 3D core. As for power consumption goes, we only have NVIDIA's word for lower power requirement, but consider ATI also use videoshader for mobile parts, I suspect NVIDIA's claim only applies to NVIDIA's own products rather than ATI's.As for multiprocessing goes, ATI better catchup. After all, not every gamer can affort Evans & Sutherland simFUSION cards.
Phiro - Tuesday, June 29, 2004 - link
Yes, but there's the economy of scale. Nvidia has a "single" production line churning out the nv4x chipset and they package them accordingly to their price point - no major modifications required.The 6800U & x800XT don't really qualify as a "halo" products - they are a high-end version of the *same product the majority of users buy.
klah - Tuesday, June 29, 2004 - link
"And the whole "alienware sells 30k systems a year so there is a market for this" - 30k video cards a year is less than a drop in the bucket for the R&D spent on putting this together."The same could be said for the 6800U and x800XT. 99.9% of cards purchased will be sub-$200, so why bother with $500+ units? It's called a halo product. They are not built to make money. They are built for bragging rights and to generate a positive brand image. The 'buzz' this product creates for Nvidia is more substantial than spending the money on magazine ads and lan party sponsorships.
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"Excuse me, but I noticed that one 6800 Ultra takes two slots worth of airspace (due to the gigantic fan). So that means the Ultras would actually occupy the first and third PCIe slots"
No. All pci-e slots are not they same. This setup require two x16 slots. Dual x16 moptherboards do not have any other slots between these. These two slots have about double the space between them as the rest of the x8, x4 and x2 slots.
Nvidia is launching their nforce4 chipset later this year which will support dual pci-e x16. This is probably when this product will become available at retail.
Phiro - Tuesday, June 29, 2004 - link
Ugh what a dumb, dumb waste of technology. Give me dual video cards (for dual directx/opengl displays) but not SLI BS. This is far better served with multiple GPU's on the card, not multiple cards.If Nvidia is really so concerned with people being able to pay for the ultimate in performance or allowing people to "upgrade" without throwing everything away, Nvidia should go with a user manageable socket on their cards and support multi-core GPUs.
And the whole "alienware sells 30k systems a year so there is a market for this" - 30k video cards a year is less than a drop in the bucket for the R&D spent on putting this together.
If this idiotic SLI re-invention cost the release of the nv4x (and prolonged our nv3x agony) a single day, or increased the cost of the nv4x cards by a single dollar, Nvidia is once again crowned king of the dumbshits in my book.
Good choice buying 3dfx, Nvidia. It took a few years but Nvidia proved the old adage "You are what you eat". Nvidia's cards are hotter, larger, more complicated and more proprietary every day.
ScuZZee - Tuesday, June 29, 2004 - link
Excuse me, but I noticed that one 6800 Ultra takes two slots worth of airspace (due to the gigantic fan). So that means the Ultras would actually occupy the first and third PCIe slots (the second and fourth slot would be made useless since it would be blocked by the coolers).So does that means the mobo have to spaced out the two PCIe slots to accommodate the two Ultras?
SpeekinSfear - Tuesday, June 29, 2004 - link
barbaryJust FYI, if you're gonna buy two, the GT model which $399 instead of the $499 Ultra cost can do it too. They're smaller, less hot and power draining, and did I mention cost $100 less. I think the only power difference is that the GT ones have 50mhz less clock speed.
barbary - Tuesday, June 29, 2004 - link
So now I am stuck what to buy.I have a 670 Dell workstation and I was going to buy an ATI X800. But now should I buy a 6800 Ultra??
Question is do I buy two so I know I have a pair??
If I do and this technology doesn't come along for months I have wasted my money.
If I don't buy two a may never get a pair to match and have wasted my money.
Swaid - Tuesday, June 29, 2004 - link
Its not like you *have* to purchase 2 video cards for anything to work, thats only for the big spending enthusiast nuts and the CG/CAD guys. Its already part of the GPU, so its like an added bonus. The hard part in the beginning is getting a motherboard to support 2 PCIe x16.