GeForce 6 series

Lore & Background

The GeForce 6 series introduced the Scalable Link Interface (SLI), allowing two GeForce 6 cards of the same type to be connected in tandem, with the driver software balancing the workload between them. SLI-capability was limited to select members of the GeForce 6 family (6500 and above) and was only available for cards utilizing the PCI-Express bus. Nvidia PureVideo technology combined a dedicated video processing core and software to decode H.264, VC-1, WMV, and MPEG-2 videos with reduced CPU utilization. Nvidia was the first to deliver Shader Model 3.0 (SM3) capability in its GPUs, which extended SM2 with standard FP32 precision, dynamic branching, increased efficiency, and longer shader lengths. SM3 was quickly adopted by game developers because it was simple to convert existing SM2.0/2.0A/2.0B shaders to version 3.0, offering noticeable performance improvements across the entire GeForce 6 line.

The first family in the product line, the 6800 series, catered to the high-performance gaming market. The 16 pixel pipeline GeForce 6800 Ultra (NV40) was 2 to 2.5 times faster than Nvidia's previous top-line product (the GeForce FX 5950 Ultra), packed four times the number of pixel pipelines, twice the number of texture units, and added a much improved pixel-shader architecture. The 6800 Ultra was fabricated on the same (IBM) 130 nanometer process node as the FX 5950 and consumed slightly less power. NV48 was a later version of NV40 manufactured in 110 nanometer process. Initial 6800 members were designed for the AGP bus; Nvidia added support for PCI Express via an AGP-PCIe bridge chip. The use of a bridge chip allowed Nvidia to release a full complement of PCIe graphics cards without redesigning them for the PCIe interface.

PureVideo functionality varied by model, with some models lacking WMV9 and/or H.264 acceleration. The first GeForce products to offer PureVideo, the AGP GeForce 6800/GT/Ultra, failed to support all of PureVideo's advertised features. Media player software with support for WMV-acceleration did not become available until several months after the 6800's introduction. User and web reports showed little if any difference between PureVideo enabled GeForces and non-Purevideo cards. In late 2005, an update to Nvidia's website confirmed that WMV-acceleration is not available on the AGP 6800.

Reader's Guide

The GeForce 6 series marked a significant generational leap for Nvidia, introducing Shader Model 3.0 support, which became a standard for DirectX 9.0c games and was quickly adopted by developers due to its compatibility with existing shader code and performance benefits. The series also brought SLI multi-GPU technology to the consumer market, though it was limited to PCI-Express cards and higher-end models. PureVideo technology represented Nvidia's push into hardware-accelerated video decoding, though early AGP 6800 models had notable gaps in support, particularly for WMV9 acceleration, which was later confirmed as unavailable. The 6800 series, as the flagship family, demonstrated substantial performance improvements over the previous generation, with the 6800 Ultra being 2 to 2.5 times faster than the GeForce FX 5950 Ultra while using similar manufacturing technology. The use of an AGP-PCIe bridge chip allowed Nvidia to transition to PCI-Express without redesigning GPUs, though it initially raised concerns about bandwidth utilization; benchmarks showed that AGP 8× was sufficient for most contemporary games, making the additional PCIe bandwidth largely superfluous. The series also saw compatibility issues with some VIA and SIS chipsets and AMD Athlon XP processors, particularly with GeForce 6600 and 6800 GPUs in Direct3D applications, causing freezing, artifacts, and reboots. The GeForce 6 series established many features that would become standard in subsequent generations, including Shader Model 3.0, SLI, and integrated video processing.

Did You Know?

• The GeForce 6 series was the first to deliver Shader Model 3.0 capability in GPUs.
• SLI-capability was limited to GeForce 6 cards 6500 and above and only available on PCI-Express bus.
• The AGP GeForce 6800/GT/Ultra failed to support all of PureVideo's advertised features, and WMV-acceleration was later confirmed unavailable on the AGP 6800.
• The GeForce 6800 Ultra was fabricated on the same 130 nanometer process as the GeForce FX 5950 Ultra but consumed slightly less power.