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The Promise of PCI Express

Graphics throughput doubles bandwidth of AGP 8X By John Virata

The introduction of PCI Express as the next standard for PC workstations has brought a shift in graphics technology that promises to give animators and effects artists access to huge amounts of graphics processing power. The standard, which will undoubtedly replace the AGP specification and other PCI graphics implementations in the near future, holds a lot of promise in mitigating some of the bandwidth issues that have plagued the PC, while enabling users to manipulate huge amounts of data without farming some of the work to the host CPU.

Each of the three big iron graphics card manufacturers are taking several approaches to the standard, with some forging into new territory with full blown families of PCI Express solutions and others hedging their bets with continued support of the AGP specification. At SIGGRAPH 2004, all the graphics chip vendors will show their own PCI Express-based graphics solutions that were announced in the last few months prior to the show. They haven't, at least not this year, completely quit developing AGP 8X based solutions, because there is a huge installed base of systems that are based on the AGP specification, and the graphics chip vendors don't want to leave these users in a bind when it comes to new solutions based on the older standard, so expect to see continued support in the near term.  

A Very Brief History
The PCI (Peripheral Component Interconnect) bus was developed in 1992 and saw widespread use on motherboards in the early to mid 1990s. The PCI bus, designed to replace the ISA bus, was a 32-bit interconnect that enabled you to add on various components such as graphics cards and I/O boards to the PC with relative ease. In the mid 1990s, Intel decided that a dedicated graphics port was a better route for graphics, freeing up more bandwidth for the PCI Bus's 132 MB/s bandwidth limitation to other compute intensive tasks.

The first AGP-based add-in cards were released in the mid 1990s (1996-97) and at the time provided 66Mhz port speeds, while eliminating the need to compete for I/O bandwidth on the PCI bus. In 1998, the AGP 2.0 specification was released and offered 1.1GB/s bandwidth, and in 2002, AGP 8X graphics cards, with 2.1GB/s bandwidth came to market.

Today, a new standard called PCI Express, based on a point to point serial connection, is set to eventually replace the PCI and AGP standard for graphics cards. This new technology allows for higher clockspeeds as well as the capability to accommodate multiple channels, or lanes for data transfer in both directions at the same time. What this essentially means is that there are more lanes on the freeway for which your data can be routed without bottlenecks inherent in the older PCI and AGP specifications. Because the PCI Express architecture is designed to be scalable, as systems manufacturers release new workstations with faster processors, memory, graphics, and networking capabilities, the PCI Express architecture, by design will scale to these new capabilities, enabling more bandwidth and data flexibility than that of PCI and more graphics horsepower than that of AGP.

In this DMN Q&A, we queried Neil Trevett, Senior VP of Market Development at 3Dlabs; Jeff Brown, General Manager of Professional Graphics at NVIDIA; and Dinesh Sharma, Director of Workstations at ATI on the current state of the graphics market and what effects PCI Express will have on the market.


Dinesh Sharma
Director of Workstations

What new technology do you hope to see at SIGGRAPH 2004?

At Siggraph 2004 ATI will be demonstrating a whole new product line-up with native PCI Express x16 lane support. Our new FireGL Visualization series of workstation graphics accelerators has been engineered to have complete, true PCI Express for increased bandwidth in both simultaneous upstream and downstream directions. The product line-up includes powerful entry-level solutions (FireGL V3100 with 128MB of memory & FireGL V3200 with 128 MB dual DVI and stereo 3D); the mid-range FireGL V5100, with 128MB of memory, dual DVI, and stereo 3D, and the high-end FireGL V7100 with 256MB of GDDR3 memory, dual DVI, stereo 3D and dual link support for ultra-high resolution displays. Our OEM and system integrator partners will be showcasing their new workstation designs with FireGL hardware driving the 3D graphics.

Datasets are getting bigger and bigger as artists push the envelope of digital effects. How is ATI working with the 3D software vendors to ensure that their applications are getting the most performance out of ATI's hardware that they can?

ATI's software engineers work closely with key ISV software development teams to the mutual benefit of our companies and customers. At one level we ensure that new features and capabilities of our hardware are fully exploited by next generation software applications. New advances in hardware accelerated rendering and the adoption of shading languages like OpenGL Shading Language and DirectX9 HLSL are working their way into both DCC and CAD applications.

FireGL V5100
How is ATI working with its end users to ensure optimum graphics output of its solutions?

ATI's driver teams work with ISVs to ensure that our driver software is optimized for specific applications. In fact part of the FireGL control panel allows users to pick the primary application they use and the driver then self configures for optimal performance.

The market has evolved from PCI to AGP and now to PCI Express. What kind of performance improvements should users expect to see over the AGP and PCI-based solutions?

PCI Express doubles the available bandwidth as compared to AGP 8X. Applications such as HD video compositing and editing which are extremely bandwidth constrained, will see an immediate benefit. Some graphics applications which are not bottlenecked currently, will run at the same speed on both AGP and PCI Express. However the added bandwidth will enable developers to incorporate new features and functions without the limitations that were in place up until now.

Do you see the market migrating to PCI Express or will the market still demand AGP and PCI-based solutions?

ATI and workstation manufacturers have whole-heartily adopted and endorsed this new design. The transition in the workstation market will very likely occur much more rapidly than in the consumer side.

What does this mean for the animators and effects artists who upgrade to the new graphics/hardware solutions?

For customers purchasing new workstations, the right solution is a PCI Express based system. Its enhanced bandwidth architecture is the right choice for maximizing the useful life of the hardware. For customers that have large investments in AGP based systems that are seeing performance bottlenecks in their graphics output, ATI also offers graphics accelerator upgrades to prolong the life of installed base hardware.

What does this mean for facilities that are pushing huge datasets via their renderfarms?

The impact on the offline rendering world will be limited until the mainstream rendering applications begin to use the VPU for rendering effects. When this happens the readback speed enabled by PCI-Express will really come into its own.

In addition to existing 32-bit platforms, system manufacturers are offering 64-bit-based systems using chips from Intel and AMD. There is the notion that 64-bit is more efficient, yet the market hasn't been demanding it yet, and on the operating system side, 64-bit Windows is still in beta. At SIGGRAPH 2005, do you expect to see all 64-bit solutions handling the modeling, texturing, and rendering operations of animation/effects shops or will we continue to see 32-bit systems churning through these datasets?

Siggraph 2005 will most likely be a hybrid of both 32-bit platforms and 64-bit. The main push behind 64-bit will come after the application vendors have 64-bit versions up and running. The obvious benefits will come with increased memory capacity and also more efficient handling of complex math tasks used in animation and rendering.  

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Related Keywords:PCI Express, AGP, AGP 8X , SIGGRAPH 2004, graphics card


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