[H]ard|OCP

Navigation

• [H] Forums
• Archives
• Search
• [H] Folding

NVIDIA SLI Upgrade Guide

Thinking about upgrading to a gaming rig powered by NVIDIA's Scalable Link Interface? We tell you what you need to know by showing you what type of gaming experience you can expect in Half Life 2, DOOM 3, and FarCry with focus on where your SLI upgrade path will lead you in terms of image quality.

NVIDIA SLI Introduction

What is NVIDIA’s SLI technology all about? To put it simply, it is using two PCI-Express video cards in tandem instead of just one. This effectively “doubles” your gaming “performance,” or at least that is what it did for 3dfx back in the first days of SLI. We think that SLI today is more about providing you, the gamer, a better overall quality of experience. Let’s face it, if speed is what you want, you don’t need a high-dollar video card for that. If what you are looking for is the most cinematic and immersive gaming experience you can get, then SLI may be right up your alley. For a full background and explanation of the SLI technology, please see our article from earlier this year. Here today we are going to discuss upgrading options and what they may provide in hopes that our readers can make the right SLI decisions for themselves.

Obviously, upgrading to a SLI capable system needs to be well thought out. First off, moving down the SLI upgrade path means only using NVIDIA video cards, at least currently. It also means purchasing specialized SLI NVIDIA video cards and a special motherboard. For those of us not wanting to buy a complete SLI system now, today’s SLI configuration leaves us room to buy “One Card Now and One Later.” We think that most people will follow the “OCNOL” upgrade path and expand to SLI as prices of additional cards come down as the market moves forward.

The Motherboard

A NVIDIA SLI setup of course requires a special motherboard with two PCI-Express slots capable of accepting SLI video cards. While we will see SLI motherboards from the usual suspects, ASUS supplied the A8N-SLI motherboard for this guide. Our A8N-SLI uses a NVIDIA nForce4 chipset recently launched by NVIDIA.

You can see above that the A8N-SLI leaves a nice space between the PCI-Express X16 video card slots for airflow. It also has a small card that clips into what is actually a PCIE mobile socket. This card is flipped around to allow the signals on the motherboard to spread out to two X8 PCI-Express sockets for SLI or to divert all that bandwidth to one X16 socket in single card usage mode. Of course both physical sockets are of the X16 spec, even though they are really operating at PCIE X8 speeds when in SLI mode.

In the last three pictures above, you can see the SLI connector that sits on top of the cards and connects to their “golden fingers.” This connection allows up to 10GB/sec transfer rate and allows the cards to “stay in sync.”

The Video Cards

Rest assured that while NVIDIA is currently the only SLI game in town, we will see a similar solution from ATI next year. So for all of our readers that bleed ATI-red blood, all hope is not lost, but for now NVIDIA has the market cornered.

But not all NVIDIA video cards support SLI. Currently the only announced products are the GeForce 6800 Ultra, the GeForce 6800 GT, and the GeForce 6600 GT. If you check NVIDIA’s website, it specifies that the “vanilla” 6800 will support SLI as well, but we are yet to be made aware of this by seeing functioning cards. We are promised that we will start seeing these PCI-Express cards showing up in retail in December, but be advised that it will really be Q1’05 before we see any great quantity of either SLI motherboards or SLI video cards on the shelves. Below is what two 6800 Ultras look like when poised in all their SLI glory.

Subsequently, while two Ultras take up a lot of room, two 6600 GTs are left with more than enough room to breath.

Video Card Compatibility

Of course there has been some enthusiast talk about just what cards will work together and what cards will not. First off you will need cards with two like GPUs. Meaning that SLI will require two 6800 Ultra, or two 6800GT, or two 6600GT video cards. We would also suggest that you look for the NVIDIA SLI Certification Logo, as explained here in this press release. While we have not yet had a chance to test retail samples, cards showing the SLI certification logo even from different manufacturers should, in theory at least, work together in SLI configurations. Meaning that a BFGTech SLI certified 6800 Ultra should work with an Asus SLI certified 6800 Ultra. Of course that is yet to be seen by us, but NVIDIA has seemed very solid on this point. This should of course make moving to a SLI configuration over a long period of time a bit more comforting in that you can find a SLI video card to work with your first purchased card.