Date:
Monday , March 24, 2008
Author:
Brent Justice
Editor:
Kyle Bennett
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XFX GeForce 9800 GX2 Quad SLI

Today we evaluate the gameplay experience supplied by Quad SLI using two XFX GeForce 9800 GX2. We play Crysis, Jericho, & CoD4 to examine real-world advantages at high resolutions and compare the Radeon HD 3870 X2 CrossFireX & GeForce 8800 GTX SLI.

Introduction

This evaluation focuses on Quad SLI performance using two XFX GeForce 9800 GX2 video cards. To learn all about the new GeForce 9800 GX2 please read here. That evaluation will provide single XFX GeForce 9800 GX2 gameplay analysis compared to GeForce 8800 GTS 512MB SLI, GeForce 8800 GT 512MB SLI, and an ATI Radeon HD 3870 X2.

To summarize, the GeForce 9800 GX2 is a single video card package with two GPUs, each on a single PCB, with SLI hardwired between. Both GPUs contain 128 stream processors clocked at 1.5 GHz and the core clocked at 600MHz. There is 512MB of RAM available to each GPU clocked at 2 GHz with a 256-bit memory bus. The result of these specifications means each GPU can be considered a lower clocked GeForce 8800 GTS 512MB GPU.

Quad SLI

In our initial evaluation we discussed the support of Quad SLI with the GeForce 9800 GX2. Indeed, the new 9800 GX2 supports this feature. You will be able to take two GeForce 9800 GX2 video cards, place them in an appropriate NVIDIA SLI capable motherboard and utilize the benefits of Quad-GPUs powering your games.

NVIDIA has come a long way with Quad SLI technology. Their previous attempts at Quad SLI left a lot to be desired. And we will not BS you, we thought highly of it when it came out, but support after that just flopped. There simply weren’t enough game profiles, meaning there were only very specific gameplay advantages in certain games using Quad SLI. NVIDIA has made huge strides in improving Quad SLI support, compatibility, and rendering modes.

Quad SLI now uses full Alternate Frame Rendering (AFR) in Quad SLI operation as opposed to the older AFR of SFR (Alternate Frame Rendering of Split Frame Rendering.) Split Frame Rendering (SFR) has some major drawbacks in efficiency and scaling the best with multi-GPU hardware. For one thing, it does not accelerate geometry data, only pixel data. AFR however, accelerates the entire frame, geometry and all. The GeForce 9800 GX2 now uses AFR across the board for the best performance scaling in Quad SLI.

Not only has the rendering methods improved, but NVIDIA has been hard at work to provide hundreds upon hundreds of built in game profiles in their drivers to support SLI and Quad SLI. If a profile does not exist the ability is there within the drivers to force AFR if you wish on at all times. In our testing here today we did not have to concern ourselves with profiles at all, every game worked out of the box with Quad SLI.

XFX GeForce 9800 GX2 Quad SLI

Quad SLI is extremely easy to setup. For our testing we utilized an NVIDIA 790i Ultra SLI based motherboard. Installation was as easy as placing each video card in the appropriate slot, placing the single SLI connector atop the video cards and plugging in all the power connectors. After this a driver installation was performed and we found Quad SLI to be enabled by default! It took only a few minutes for the whole process from installing the video cards to installing the drivers and gaming in Quad SLI.

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On our motherboard we could place the video cards a PCIe slot apart from each other, so they had plenty of room to breathe. The video card that acts as the primary display video card will light up with a blue LED. Note that multi-display does not work with Quad SLI enabled; you must disable Quad SLI to use multiple displays. In the driver control panel there is an easy radio button selection to choose Quad SLI or Multi-Display. You can also enable the “SLI indicators” to see Quad SLI in action working in your games. We turned this feature on and noticed Quad SLI doing its thing in every game we tested today. Multiple display support with multi-GPU configurations is support by AMD’s Radeon CrossFireX. NVIDIA needs to do the same, but is being stubborn about it for some reason.