SiS Xabre400 review

Motherboards supporting AGP 8x are due for release soon and, as scene complexity increases, this feature should provide performance benefits. However, most current games aren't designed to work with the AGP 4x specification, so it remains to be seen if AGP 8x will provide benefits to today's software.

Another aspect that's become standard on modern graphics accelerators is anti-aliasing. The Xabre400's Jitter-Free Anti-aliasing subsystem supports 1x, 2x and 4x modes labelled as Performance, Normaland Quality.

However, unlike more sophisticated approaches, such as Nvidia's multisampling Accuview system (see Labs, issue 93, p86), that attempt to minimise performance losses, the Xabre400 uses an optimised Super Sampling approach. This essentially renders the scene internally at a higher resolution before filtering to the display resolution. While this effectively reduces jaggies, it requires considerably more bandwidth and GPU power, reducing performance. This was clear from our test results; none of the four tests achieved the minimum playable average of 30fps with 4x anti-aliasing enabled.

Other features common to current 3D cards include FMC (Frictionless Memory Control). In a similar manner to Nvidia's LMA (Lightspeed Memory Architecture), this is designed to improve memory bandwidth usage by using methods such as hidden surface removal. SiS has also added a feature called Coloredeemer, which is similar to Nvidia's Digital Vibrance Control in that it enhances colour rendition.

Perhaps the most unusual features, however, are accessed through a separate utility. Using this utility, you can play games in Wireframe or Transparency mode, which simply makes 3D objects translucent. The utility also provides overclocking functions and allows use of 3D glasses.

Even though 3D features have stolen the limelight in modern cards, 2D features such as DVD playback and multimonitor support have also become popular. SiS has recognised this and incorporated many of them in to the Xabre400 design.

The primary display is driven by a 24-bit colour 375MHz RAMDAC, capable of resolutions up to 2,048 x 1,536. Dual monitor support is provided thanks to the inclusion of an SiS 301 companion chip. This allows for a variety of dual-display setups, including digital flat panels via the DVI interface and TV-out via the S-Video output. The typical mirroring and display spanning options are available, and the driver even allows you to select the split of video bandwidth between the two displays.

On the video front, there's the MotionFixing video processor, which includes motion compensation and iDCT for hardware-assisted DVD decoding, plus scaling and adaptive deinterlacing. This worked well in our tests, although DVD playback quality was merely average, with some minor deinterlacing artefacts.

Deciding which new graphics card to buy has never been easy, with new boards appearing every six months. However, if you don't want to pay an exorbitant price for a high-end card, the Xabre400 would appear to offer excellent value for money, with DVD, dual display and Pixel Shaders. That said, performance is average, particularly OpenGL and there may be some issues with the early drivers, although this should improve with time.

The Xabre400 is a promising start for SiS. And with a faster version, the Xabre600, due soon and DirectX 9-compliant products set for the end of the year, it looks like the company is here to stay. If £76 is all you have to spend, the Xabre400 offers more than the GeForce 4 MX. However, if you can afford a little more, go for Gainward's GeForce4 PowerPack! Ultra 650 TV/DVI or Hercules' 3D Prophet FDX 8500 LE, which offer better performance and hardware Vertex Shaders.

Author: Gareth Ogden