etitors are including 3-D functions in their new processors, which will further splinter a fragile industry graphics standard.
AGP Takes Hold
Three-D performance is tied directly to the power of the CPU that must process the geometry setup before sending data to the graphics chip. New graphics pipelines such as Accelerated Graphics Port (AGP) are significantly expanding the graphics bandwidth. Proposed by Intel, it designed AGP to move large texture maps from system memory onto the board's graphics memory quicker. AGP includes two basic modes of operation for rendering: local texturing (DMA mode) and AGP texturing (execute mode).
By using the AGP texturing mode, textures are executed from system memory in a one-step process. By comparison, local texturing uses a two-step process that executes textures from graphics memory through the PCI bus. At the lowest level of protocol, called 1X mode, the AGP s
ubsystem will operate as a 66-MHz PCI device for all data transfers. A 2X mode permits an effective 133-MHz operation by sending data on both the rising and falling edges of the 66-MHz clock. According to Richard Chou, graphics line manager at Leadtek, without special protocols and full driver support, texturing done in 2x AGP mode is similar to PCI (see the sidebar "AGP--When and Why?"). Several graphics chip and board makers, such as ATI Technologies, 3Dlabs, Trident Microsystems, Nvidia, and Silicon Integrated Systems (SiS), have introduced AGP solutions, and many support the 133-MHz 2X mode.
Over the years, workstation companies have refined the method for processing 3-D graphics. The images are displayed as a series of triangles, with the host processor calculating where each vertex will appear on-screen and how they will be lit and/or shaded. The system includes a rendering engine and a setup engine. The setup engine is the processor that calculates how many scanned lines of vertical resolution wi
ll appear in each triangle. Then the rendering engine fleshes out the 3-D space by painting the appropriate 2-D pixels within the triangle to fool the eye into thinking the 3-D object exists.
Intel Joins the Race
Intel, a major supplier of chip sets and motherboards, is becoming more involved in graphics chip development. In July, Intel agreed to purchase Chips & Technologies (C&T), a leading manufacturer of graphics chips for notebook PCs. Intel, C&T, and Real3D, a Lockheed Martin company, have been jointly developing the upcoming Intel 740 graphics chip, code-named Auburn, for desktop PCs and workstations.
All the graphics card companies in Taiwan are scrambling to embrace Intel's graphics technologies by introducing reference boards. Major makers such as Asustek, Leadtek, and Gainward gave OEMs a sneak peak during last fall's Comdex. Mass production of Auburn-based units will begin in early spring.
Other vendors, including ATI, Trident, and SiS, have taken a different
tack with the next-generation multimedia accelerator processors. These mixed-signal devices for both 3-D graphics and digital versatile disc (DVD) playback are designed to off-load multimedia processing tasks from the host CPU. Some are meant to handle a bundle of multimedia processing tasks.
Designed with robust support for Intel's AGP, the 3-D Rage Pro chip from ATI includes a triangle setup engine with improved perspective correction and transparency implementations. Also, the controller supports complex texture mapping and filtering, z-buffering, double buffering, and Gouraud shading, plus special effects such as alpha blending and fog.
CPU-Level Support
The CPU greatly affects 3-D performance, because it still handles most of the geometry processing for today's accelerators. MMX-enabled (multimedia extensions) CPUs can provide an additional performance boost in certain audio and graphics tasks through the use of special instructions and by having one instruction act on several data
sets. Although you can certainly perform these tasks on Pentiums without MMX technology, they are rendered much more slowly.
In an unexpected attempt to steal the thunder from the forthcoming MMX-2 instruction set, Cyrix and AMD outlined a different, and incompatible, set of multimedia instructions to be added to a forthcoming microprocessor generation. Intel's MMX-2 instructions are earmarked for the company's Katmai, a processor expected in early 1999, according to Taiwan's motherboard makers.
The additional multimedia instructions from both Cyrix and AMD are designed to accelerate geometry and reduce the number of calculations by employing a capability of Direct3D, a part of DirectX, that is called
immediate mode
, in which the code is largely crafted by the application vendor. Cyrix's new MXi, which it will release by the second half of the year, will be the first processor based on the company's upcoming Cayenne processor technology. Cayenne is designed to compete with Pentium II proc
essors and deliver the equivalent performance of 300 to 400 MHz.
Cayenne, which is targeted at desktop PCs that are priced under $1500, will feature a fully pipelined, dual-issue FPU and 15 new MMX floating-point instructions to enable high-performance 3-D graphics, DVD, and 3-D audio applications. A key component of the Cayenne core will be the processor's ability to execute 4 floating-point operations per cycle using a dual MMX unit, letting the device deliver 1GFLOPS.
Meanwhile, AMD says that it will incorporate a new host of 3-D instructions into the K6. The new instructions should accelerate graphics processing and improve video playback on MPEG-2 using a new instruction set developed by AMD and supported by Microsoft's DirectX. Code-named Chompers, samples of the new chip have been shipped to AMD development partners.
Stella Kao is a BYTE contributing editor based in Taipei. You can reach her at
meou@email.gcn.net.tw
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The Third Dimension
