Intel's Accelerated Graphics Port
AGP is a connector specification, a new video standard and a new way of handling graphics on your computer's bus. Its 133MHz speed represents a large increase over the current 33MHz PCI standard. Initially, it will be offered only on computers that use one of the new Intel Pentium II processors. Systems based on these processors with AGP support should ship later this year.
Since AGP requires special core logic and will use a different edge connector from the one today's PCI cards use, it's unlikely the technology will be offered as an upgrade for existing desktop computers. System vendors will offer AGP in two configurations: some will use add-in cards and others will socket AGP directly on the motherboard.
Why AGP?
AGP doesn't simply speed up graphics; it paves the way for qualitative improvement of them. In today's 3D action games, for example, the play is almost always fast, but moving objects and surfaces must dwell within a couple of megabytes on the graphics card--enough memory for blocky, blurry visuals only. Allow the graphics card to access main system memory through a fast AGP slot, and game developers suddenly have room to pile on detail without slowing performance.
Some PCI-based graphics accelerators have begun using host-based memory to store textures. Still, AGP offers even more advanced features. "Pipelining" enables multiple requests to be queued while others are being executed. Previously, cards operated on a relay-race-like model--a piece of data had to return before the next request could go out. The STB Velocity 128, the Diamond Viper V330, and the Cirrus Logic Laguna 3D-AGP all support pipelining.
A card that supports "sideband" addressing provides a separate channel for memory requests, so graphics data can blast through, uninterrupted. And 2X cards will double the throughput in some operations, although Intel admits that the perceived difference will be much less than two times the speed. ATI stands as the only manufacturer to currently support the full set of AGP features with its 3D Rage Pro accelerator, which is found on its Xpert@Home and XPert@Play cards. However, early tests show that the current 2X AGP brings little benefit over baseline and even PCI solutions. In late 1998, Intel plans to release a new 4X version of AGP. Expect cards that support 4X soon after.
AGP will improve the performance of virtually all graphics-intensive applications. Intel sources claim improvements could be as great as 30 percent, but graphics board suppliers, like Diamond Multimedia, estimate an increase of about 15 to 20 percent. However, because the technology is scalable, the more video memory and system memory your new computer has, the better its performance. And the difference could be much greater than 30% where large textures are involved.
AGP is a physical data-transfer pipe that connects the video controller back to memory. It allows your system to dedicate unused system memory and bandwidth to processing graphics. In other words, with AGP your graphics board can access your main memory for as much room as it needs. The AGP bus comes directly out of the core logic chipset. Intel says it has up to 10 times the memory bandwidth of the traditional PCI bus. Although AGP operates at a clock speed of only 66MHz, it sustains most of its operations on the two edges of the clock cycles, where it transfers 4 bytes (32 bits) of data at twice that speed, up to 133MHz.
A typical AGP-enabled system will include a Pentium II or AMD K6 processor, a 3GB hard drive, an AGP graphics card with 2MB or 4MB of VRAM and 1024x768 video as its native resolution, 32MB of SDRAM, up to 1MB of level 2 cache and Microsoft's Windows 95/98 or NT 5.0 operating system.
Speed at Any Cost?
AGP's cost will depend on the type of system you use. If you buy a new 233MHz or 266MHz Klamath-equipped desktop with a motherboard from Intel, AGP will be built in. If you purchase a system with an empty AGP connector and decide to move to this technology, you'll need an appropriate add-in card. Initial offerings are coming in at under $200 US with 4 MB of Ram.
Main Back
© 1997 - 2000 COMBATSIM.COM, Inc. All Rights Reserved.
Last Updated August 30th, 1997