NVIDIA® SLI™ Technology FAQ

General Questions

What is SLI? How does it work?
SLI™ or Scalable Link Interface is a high-performance technology that allows users to intelligently combine and scale graphics performance by having multiple NVIDIA® GPUs in a single system. SLI works by intelligently scaling geometry and fill rate performance for two GPUs.

Does SLI work on AGP?
No. SLI is designed for PCI Express.

How does SLI work on PCI Express?
SLI is designed for PCI Express. This new bus has superior bandwidth (two to four times AGP 8X), support for isochronous data transport, and the capability to drive multiple high-speed graphics devices. AGP 8X was limited to one high-speed graphics device and was not a good candidate for SLI.

What cards can work together in an SLI configuration?
All PCI Express based GeForce 6800 Ultra boards support SLI technology. Boards must be the exact same model number and from the same vendor – for example, two GeForce 6800 Ultras from Vendor XYZ.

Can I mix and match?
No. NVIDIA doesn’t support SLI on two different models or from different vendors. SLI supports configurations with the same model (i.e. 6800 Ultra) from the same vendor (Vendor XYZ).

Where, when, and from whom will end users be able to buy SLI consumer graphics boards?
Initial availability will be from enthusiast PC manufacturers. Retail versions of SLI-bundled graphics boards will be announced later this year.

How is SLI different from competitive product offerings?
SLI takes the PCI Express multi-GPU configuration to the next level by designing a family of GPUs that feature intelligent patent-pending hardware and software technology. The result is never-before-seen performance on PCs and workstations.

Do you have dedicated hardware for NVIDIA SLI or is it just software?
We have dedicated scalability logic in each GPU and a digital interface between GPUs to help enable this. In addition we have a full software suite that enables dynamic load balancing and advanced rendering algorithms that provide the best image quality.

How does this technology differ from 3dfx’s SLI?
NVIDIA SLI differs in many ways. First, 3dfx SLI was implemented on a shared bus using PCI. The PCI bus delivered ~100MB/sec. of bus throughput, while PCI Express is a point-to-point interface that can deliver ~60× the total bandwidth of PCI. Second, 3dfx SLI performed interleaving of scan lines, and combined in the analog domain, which could result in image quality issues due to DAC differences and other factors. 3dfx Voodoo technology also only performed triangle setup, leaving the geometry workload for the CPU, hence 3dfx SLI only scaled simple texture fill rate, and then used inter-frame scalability. NVIDIA SLI technology is PCI Express based, uses a completely digital frame combining method that has no impact on image quality, can scale geometry performance, and supports a variety of scalability algorithms to best match the scalability method with application demands.

How will applications take advantage of the SLI technology?
SLI technology is application transparent and is enabled through the graphics drivers. All DirectX and OpenGL applications can take advantage of SLI. When two graphics boards are configured with SLI technology, applications will automatically be able to take advantage of performance improvements with no modifications.

How much of a performance increase will I see with SLI technology?
The amount of performance improvement will depend on the application. In some circumstances it is up to a 2X increase in performance. In general, applications running at higher resolutions with higher image quality settings will benefit most.

Will SLI be a standard feature from NVIDIA from now on?
SLI will be offered on certain high-end PCI Express product offerings from NVIDIA going forward. The current products that support this are the PCI Express versions of the GeForce 6800 Ultra.

What operating systems will be supported?
32-bit and 64-bit Windows and Linux OS (when available).

Configuration Questions

Which systems support SLI technology?
Alienware Area-51 ALX SLI systems are specifically designed to support multi-GPU technologies such as NVIDIA's SLI. Area-51 ALX SLI systems feature the Alienware X2 SLI-ready motherboard with dual PCI Express x16 physical connectors. These connectors accommodate validated NVIDIA-based SLI-capable GPUs. Furthermore, given its advanced liquid cooling system and 650-watt SLI-ready power supply, Alienware Area-51 ALX SLI systems provide the ultimate foundation for the massive performance enabled by NVIDIA SLI Technology.

Can SLI work with one PCI Express board and one AGP 8X board? What about PCI Express and PCI?
No. SLI is designed solely for PCI Express.

Can you do more than two boards with SLI?
We are currently only introducing dual GPU scaling at this time.

Do I need special drivers?
No. NVIDIA’s ForceWare Unified Driver Architecture with support for SLI will come pre-installed in PC manufacturer’s systems. These drivers will be posted on nvidia.com when retail versions of the products are available.

Will all board manufacturers support it (SLI connector)?
Every high-end PCI Express reference board from NVIDIA will support SLI. It will be up to the add-in-card partner to determine if they follow NVIDIA’s reference design. The current products that support this are the GeForce 6800 Ultra.