AGP--When and Why?

Like multimedia extensions (MMX) technology, Accelerated Graphics Port (AGP) will become important down the road. Using the AGP connection, the graphics chip can access system memory directly through the system chip set at memory-bus speeds, reducing latency and increasing performance compared with PCI transfers. Doing so removes the burden of graphics throughput from the PCI bus. With AGP, software developers have more graphics bandwidth to work with, and future applications will certainly require AGP.

While all major vendors have announced AGP-compliant solutions, a few mainstream graphics chip vendors such as S3 say they will wait until Windows 98 is out to fully support AGP. By then, Pentium II systems are also expected to be more prevalent. Software applications have yet to take advanta ge of AGP. Software applications with textures large enough to require AGP will begin arriving only in the first and second quarters of this year.

Asustek's associate vice president for R&D, H. C. Hung, says that today many AGP graphics boards show minimal performance gains over PCI offerings. "Our test result shows that only 350-MHz and up Pentium II processors with the Intel 440BX chip set can bring the AGP performance into full play," he adds.

More recently, there is an ongoing debate about enhancing performance by adding AGP or a larger frame-buffer memory. Because AGP uses part of the existing system memory for MIPS-ma pping textures, one of its advantages is that it should require less memory on a graphics card for a less expensive solution. However, many makers agree that the cost of adding an AGP graphics accelerator is still less than adding an additional 4 MB of local graphics memory.