Graphics controller delivers 8x AGP performance

Silicon Integrated Systems Corp (SiS) is well known as a Taiwan supplier of core logic. With its Xabre400 GPU, SiS is trying to break into the mainstream graphics market also, going head-to-head with the likes of Nvidia and ATI and bidding for a market defined by “hard-core” gamers and the need for ever-higher levels of 3-D realism. The PC industry is waking up to the threat of the X-box, and other games consoles, where it must deliver competitive performance or fall behind.

The Xabre400 GPU supports AGP 8× graphics processing, is optimized for the DirectX 8.1 API, and gives you 2.1-GHz bandwidth.

The Xabre400 is clearly a move in that direction—a single-chip solution delivering 8× performance on the AGP (accelerated graphics port) bus, while optimized for graphics processing for the DirectX 8.1 API. Thomas Tsui, director of the Multimedia Products Division at SiS, emphasizes that this video processor has been optimized for pipeline efficiency, processing at 4P8T (four pixels and eight texils) each timing cycle. Usually, says Tsui, a mainstream GPU will only handle 2P4T per clock or only 50% of the efficiency achieved by SiS’s new product. What this chip represents in terms of architecture is GPU bandwidth at 2.1 GHz, eliminating the data bottleneck that occurs when the GPU can only achieve a bandwidth of 1.0 GHz. With PCs now

delivering data at 2.4 GHz between core logic and main memory or CPU, graphics processing must achieve comparable throughput or place a drag on system performance. A bandwidth of 2.1 GHz also brings the PC into line with dedicated games boxes.

Tsui also emphasized that the new GPU supports a third-generation T&L (transform and lighting) engine, supporting up to 16-vertex cache, the highest level in the mainstream graphics market.

SiS is bundling its proprietary CubicLook utility with the processor, supporting the use of LCD headsets. This utility can also assess, through the use of a ring oscillator, parameters for safely overclocking the chip, according to environment and configuration. Adjustments are made to the memory clock and the engine clock, according to feedback from the ring oscillator.

When coupled with SiS’s 301 device, this processor will also support dual scene display, when output is both to a monitor and a TV, for example. Applications might include corporate spreadsheets. Tsui pointed out that TV circuitry is mainly analog, so voltage requirements and the need for a wide noise margin make it preferable to have TV-out functionality on a second chip (the 301), rather than integrated on the processor.

The core and memory of this GPU are at 250 MHz (500 MHz DDR). The device provides a 128-bit DDR memory interface and supports up to 128 MB of video memory.

Currently the SiS GPU is sampling to card makers, with well over a dozen having shown strong interest.


SiS (Silicon Integrated Systems)
Fax (886) 3-577-8774
www.sis.com