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When we talk about Quad SLI we talk about performance right ? Yes in essence that is true as everything boils down to performance in this segment of the market, but in the case of Quad SLI is more about distributing that high performance level for image quality options. Confusing ? Let me explain..

This is something you really need to keep in mind. Quad SLI gaming is intended for people that game at XHD (extreme high-resolution 2560x1600) and play there games with extreme high AA levels. If you plan to play games at 25x16 without high AA levels  then Quad SLI would be a serious waste of money for you. The thing is .. that second GX2 pretty much for 90% of the games is mainly used for it's SLI AA functionality (special Antialiasing modes for SLI setups). There are very little games (in fact we found only one) that will fully utilize the four cores for the actual 3D render engine as there is a limitation.

We learned that this limitation is more a DirectX9 issue rather than game engine compatibility. DX9 restricts the number of back buffers that can be queued. So in basic working, Direct X will not allow 4-way AFR which is what we really need for it to make that happen, so the solution falls back to AFR of SFR in some cases or 2-way SLI in others with D3D apps.

AFR - Alternate Frame Rendering. Each graphics core is rendering a frame at a time, odd and even. The full frame is prepared by the CPU and forwarded to the driver, which makes it render on each device to render a frame in turn. This is interleaving. First card A does a frame then card B the other.

Although NVIDIA currently is working on a DX9 bypass for this issue the approach from NVIDIA had to be slightly different than normal until that issue is resolved. Since you have two graphics cores that need something to do .. the focus really is shifted towards additional AA levels with accompanied performance increase. To do so NVIDIA is bringing special SLI AA levels towards the Quad SLI gamer. So NVIDIA offers you three SLI anti-aliasing modes for Quad SLI:

• 8x SLI-AA
• 16x SLI-AA
• 32x SLI AA (new for Quad SLI).

The usual 8x and 16x modes are provided by all high-end SLI-capable cards, new is a special 32xAA mode thats only one of its kind for Quad SLI. With the horsepower of four GPUS dividing it's power you can see some performance increases in these AA modes. To get you an idea, 8xSLIAA with 16xAF enabled is roughly 80% faster than "normal" 8xAA with 16xAF if it's compatible with the game that is.

And thus that's where the fruits of all this labor needs to be found. So if you are stuck at 1600x1200 or 1920x1200, Quad SLI probably isnt for you if you plan on gaming at 4xAA/16xAF. Simply go for high-end SLI like the GeForce 7900 512 MB GTX SLI which would offer you better performance.

How to setup Quad SLI

I wanted this article to be some sort of small do-it-yourself guide, so let's talk a little about installation.

Well ..  I really have to give props to NVIDIA here as hard and software installation simply is a breeze. Obviously assemble your PC, I won't go into details here as hey .. you are a guru, you do it on a monthly basis right ? :) But once you have your system ready you can have Quad-SLI powered up and ready to roll within a minute as it really is that easy to do.

Basically there are six steps you need to take. Here's what you need to do:

• Ready your PC, make sure all the latest mainboard, peripherals and OS drivers are up-to-date
• Insert cards into PCI-Express slots
• push SLI bridge on the GeForce 7950 GX2 (GX2 from now on) cards
• Connect 12v 6-pin PSU connector to each card (make sure each 12v connector is on a different 12v rail)
• Boot PC, install ForceWare 91.37 driver
• reboot system and voilla ...

Let's have a look at that.

As you can see we prepped the mainboad already. We have some the fastest DDR2 memory that money can buy, the Core 2 Duo X6800 processor and the Asus P5N32-SLI SE Deluxe mainboard. So at this stage we insert the first GX2 card onto that ASUS mainboard. We hook up the monitor.

The next step is simple. We add the second GeForce 7950 GX2 card and place the SLI bridge onto the SLI connectors. That's it. No BIOS changes or anything where required.

We now boot up windows, install the ForceWare 91.37 driver. After the driver installation and once you have rebooted that's it .. Quad SLI will be enabled for you at default. You startup your game, make sure you play at the highest resolution possible (2560x1600), select niche AA-SLI options in the ForceWare drivers and you are good to go. This really is all there is to it folks. I have to congratulate NVIDIA on this fool-proof setup procedure.

Easy as counting 1-2-3, Quad SLI is automatically enabled for you.