Date:
Wednesday, July 19, 2006
Author:
Kyle Bennett
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NVIDIA Quad SLI DIY Interview

We have an exclusive interview with NVIDIA about their launch into true enthusiast Quad SLI. Today marks the release of the beta driver with official DIY Quad SLI support. We ask some tough questions and get no-nonsense answers that should help you make your Quad SLI decision.

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5. Is NVIDIA overseeing and controlling all production on the 7950 GX2 currently? Will add in board production be allowed to be under the control of your partners or is the buying public to remain under the assumption that all 7950 GX2 cards are “all the same,” without regards to badging obviously.

GeForce 7950 GX2 is a product that NVIDIA sells direct to its partners. NVIDIA plans to continue with this model for this product; however, partners can make modifications to the product.

6. Obviously anyone that has the budget, has been able to build their own Quad SLI rig for a while now, but it has not been officially supported by NVIDIA. Given that today marks the release of the beta Forceware driver that supports Quad SLI, what games exactly will be supported by Quad SLI with this new driver.

Quad SLI rendering algorithms work with the existing SLI game profiles. The full list of these games can be found here. As with SLI today, applications which tax the GPU will see the greatest performance improvements using Quad SLI technology. In order to move the workload onto the GPU, NVIDIA recommends using Quad SLI at extreme high definition resolutions with high levels of antialiasing and anisotropic filtering. Quad SLI technology isn’t for everyone. NVIDIA has put together this chart to help its customers decide which platform is right for them:

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7. Out of these Quad SLI supported games, which ones are showing the best real-world scaling benefits in terms of higher IQ and/or performance that is achievable? So to put it simply, which games are the ones that will really “blow me away” when I move from a single GPU or SLI setup to Quad SLI?

The sweet spot for Quad SLI on today’s hottest games (F.E.A.R, Quake 4, Prey, Battlefield 2, Far Cry, Doom 3, Half-Life 2 Lost Coast, etc.) is 2560x1600 with SLI8x antialiasing and 16x anisotropic filtering. At this setting, you will see from 30% to 80%+ gains compared to dual GeForce 7900 GTX graphics cards.

8. Conversely, what games are not going to benefit from moving to Quad SLI? What gamers are better off with single GPU or SLI configurations? Tell us what gamers don’t “need” Quad SLI in order to help the DIYer make a good decision for his next upgrade.

The decision to move to Quad SLI should be based on an insatiable desire to game at the highest possible resolution and quality settings. In general, gaming at these settings will produce significantly faster frame rates with Quad SLI. Outside of the SLI antialiasing modes, for example 2560x1600 4xAA/8xAF, the benefits of Quad SLI are significant in OpenGL games but often less prominent in Direct3D games. It turns out that DX9 doesn't support queuing of enough frames using standard D3D API programming practices (that would attain WHQL certification) to effectively support high-performance 4-way AFR mode used in Quad systems. Quad SLI instead uses "AFR of SFR" for many D3D games. In the future with DX10, we expect 4-way AFR to work as effectively as it does with OpenGL today.

9. We saw the 7950 introduce much slower GPU and memory speeds compared to a 7900 GTX. I can understand pulling in the GPU due to power and heat concerns in such a small package, but why was the memory bandwidth pulled in from 1.1ns part to 1.4ns? Was this due to power/heat as well?

The primary motivator was power and heat, as you mention. Faster memory requires both higher voltage and higher frequencies, both of which increase thermal output. A secondary consideration was board size; less real estate provided less room to optimize memory traces.

10. Cooling is very important to the enthusiast. How much heat/wattage does a Quad SLI set of 7950 GX2 video cards dump into the case under full load? These cards do exhaust into the case, and not out the back, correct?

The thermal output of a pair of 7950 GX2 cards is commensurate with any setup that requires 284W max power total (142W per board). The cooler design exhausts air toward the rear of the case, so some of the heat is expelled through vents in the bracket. However, as you suggest, most of the heat stays in the case and good case cooling is essential.

Thanks to NVIDIA for this exclusive interview, we certainly will be following up this with discussion in our forums.

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