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Electronic Design

Graphics ICs Advance To Near-Cinematic Levels For The Computer

Upgrades in their architectures along with the integration of large buffer memories enable the new breed of graphics ICs to deliver supercomputer-like graphics performance on a single chip.

Upgrades in their architectures along with the integration of large buffer memories enable the new breed of graphics ICs to deliver supercomputer-like graphics performance on a single chip.

Today's computers can generate movie-quality 3D animation, a task that would have required days of rendering on multiple supercomputers only half a decade ago. To improve this far, many different technologies—high levels of chip integration, high-performance memories and host processors, and powerful graphics algorithms—had to join together.

The latest crop of high-end graphics engines packs close to 50 million transistors—even more than what some CPU chips have today, like Intel's Pentium 4 or AMD's Athlon families. The graphics chips are high-performance computers in their own right. They contain multiple pipelines to handle the pixel operations, as well as other computational units to perform shading, lighting, reflection, and other functions needed to produce amazingly realistic images and animation.

Many new laptop computers can deliver 3D graphics capabilities comparable to most desktops. That kind of performance is becoming a necessity rather than an option as many users view the laptop as a desktop replacement.

The once-crowded field of standalone graphics chips has condensed from over 30 suppliers to just a handful, with ATI and nVidia leading the pack. The survivors include Matrox, the S3 division of VIA Technologies, Silicon Integrated Systems, and Trident Microsystems. At the same time, manufacturers of PC motherboard chip sets are incorporating high-performance graphics engines right on the motherboard logic chip. The Intel 845G chip set is an example of that trend.

Nowadays, double-data-rate synchronous DRAMs (DDR SDRAMs) with clock speeds of 333 MHz and faster are used in frame buffers that deliver data bandwidths of 5 to 10 Gbytes/s to the graphics. The Rambus RDRAMs also provide a high-bandwidth memory interface but have met with limited success in the highly cost-competitive graphics market. Still faster memories are also being adopted—the 2G DDR SDRAM, with clock speeds starting at 400 MHz and increasing to at least 600 MHz over its lifetime, is starting to appear.

Today's host CPUs and chip sets support clock speeds of up to about 2.5 GHz, with even faster processors expected. Motherboard chip sets are also starting to offer AGP 8X interfaces to provide a 2-Gbyte/s interface between the PC and the graphics card. This will facilitate faster transfers of data into the frame buffer or other buffers on the graphics chip.

In addition to running the graphics-intensive applications, the CPUs handle many graphics support and interface functions. The combined compute power of the CPU and the graphics chip also leverages advances in software drivers, like Microsoft DirectX 9.0 and the latest OpenGL enhancements, to deliver more features and programming flexibility. To achieve supercomputer-like throughput, graphics-chip vendors have turned to extremely high levels of integration, combined with very wide databuses.

ATI Technologies' recent Radeon 9700 PRO graphics engine incorporates eight parallel rendering pipelines and four parallel geometry engines, a 256-bit wide DDR memory interface, and AGP 8X graphics support.

Those features coalesce with the company's Smartshader 2.0 technology, offering programmable pixel and vertex shaders with 16 textures per pass. The pixel shaders handle up to 160 instructions and can use floating-point precision levels of up to 128 bits for a greater range of colors and brightness levels. Vertex shaders can handle up to 1024 instructions with flow control.

ATI's Smoothvision 2.0 technology performs full-scene anti-aliasing and anisotropic filtering to improve image quality. Incorporated on-chip are a three-level hierarchical Z-buffer, as well as a video shader that seamlessly integrates the pixel shaders with video. The chip's Fullstream video deblocking technology delivers sharper looking images and packs noise-removal filtering to clean up captured video.

Archrival nVidia's recent family of graphics processors targets three market tiers: the GeForce 5800 for the high-end gamer, the GeForce 5600 for the mainstream user, and the GeForce 5200 for cost-conscious users. Each is based on the company's FX graphics-processor-unit architecture. The chips get their high-end performance from a rendering engine that works on eight pixels every clock cycle. The engine employs 128-bit floating-point precision throughout the graphics pipeline.

The FX architecture's Intellisample technology provides high-speed anti-aliasing, adaptive texture filtering, an advanced loss-less compression capability for both color and Z-data, and a fast Z-clear capability. An available Digital Vibrance Control helps sharpen images and offers enhanced color controls.

Based on this architecture, the FX 5600 delivers about 30% better performance at about half the price of nVidia's antecedent GeForce Ti4600. By removing some of the acceleration features, the FX 5200 graphics engine will let card vendors offer a full graphics adapter compatible with DirectX 9.0 for just $79.

Competing with both the ATI and nVidia solutions is the just-released DeltaChrome family from S3 Graphics. At the high end, the DeltaChrome F1 can deliver performance to satisfy most gamers, with an eight-pipeline graphics engine. Boasting a similar engine, the DeltaChrome S8 suits mainstream graphics needs (see the figure). Each pixel pipeline packs a 128-bit 3D engine, so either the F1 or S8 can deliver an aggregate fill rate of up to 2.4 Gpixels/s. Featuring a 128-bit wide interface to DDR memories, the chip achieves a peak bandwidth to memory of 11 Gbytes/s. The DeltaChrome S4, a slightly lower-performance version with four pixel pipelines, targets the more cost-conscious user.

Both pixel and vertex shaders are included, offering features beyond those required by DirectX 9.0. S3's proprietary Advanced Deferred Rendering technology is integrated into the design, which the company expects will dramatically increase the efficiency of the 3D engine performance beyond standard z-culling technology. The programmable floating-point render target and blending features will set a new bar for accuracy and quality in 3D effects.

Though not as high-performance as the previous three companies' offerings, Silicon Integrated Systems' Xabre family should satisfy many users. The top-of-the-line Xabre 600 packs a 256-bit 3D graphics engine and a motion-compensated MPEG I/MPEG II controller. It includes four programmable pixel-rendering pipelines and eight texture units. It supports DirectX 8.1 and pixel shader version 1.3. Also, it performs bump mapping, cubic mapping, and volume textures, as well as effects like transparency, blending, wrapping, mirror, clamping, fogging, and alpha blending. The memory interface can support up to 128 Mbytes of 300-MHz DDR SDRAMs. The lower-cost Xabre 400 operates at 250 MHz (as opposed to the 300-MHz Xabre 600) and delivers lower graphics performance.

The XP4 graphics engine line from Trident Microsystems targets the mainstream graphics user. The XP4 T3 supports 128 Mbytes of 700-MHz DDR SDRAM on a 128-bit bus. The midrange XP4 T2 supports 64 Mbytes of 500-MHz DDR SDRAM with a 128-bit bus. And, the XP4 T1 cuts the bus on the T2 down to 64 bits.

The XP engine includes several proprietary schemes. The SmartTile tile-based rendering maximizes memory bandwidth. De-interlacing provides adaptive display of interlaced video. BrightPixel, a 3D graphics architecture, delivers high performance with minimal transistor count.

Matrox's Parhelia512 graphics engine is used in the company's top cards. The chip uses about 80 million transistors to implement a 512-bit graphics processor and a 256-bit wide interface to DDR memory. The memory interface can address a frame buffer of up to 256 Mbytes.

Due to the wide memory bus, data can flow at transfer speeds of up to 20 Gbytes/s, the highest bandwidth of any graphics engine to date. Matrox also incorporated its Glyph anti-aliasing technology to sharpen image quality, Gamma correction to improve video playback, texture filtering to provide more realistic images, and real-time color adjustment to produce natural-looking images.

All of these engines deliver near-cinematic graphics, marking the beginning of a new era. And as the top-of-the-line devices do even more, the cinematic quality of today's high-end engines will migrate down to mainstream and low-cost systems, ultimately becoming the "basic" feature set offered by all systems.

ATI Technologies Inc. (905) 882-2600
Intel Corp. (408) 765-8080
Matrox Electronic Systems Ltd. (514) 822-6300
nVidia Corp. (408) 486-2000
S3 Graphics Inc. (510) 687-4900
Silicon Integrated Systems Inc. (408) 730-5600
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