Technology Overview
One of the marketing features used by SiS, quite understandably, to promote their range of cards is the 8x AGP compliance. Over the past few months we've seen a steady trickle of chipsets supporting this faster AGP speed, but what does it mean in the practical sense ?. Having the ability to push 2.1GB/s over the AGP bus may count for something once games become more complicated in nature, but the present AGP 4x specification, pushing just over 1GB/s, is more than ample for any of today's titles. Benchmarking with a host of titles has shown 8x AGP to offer no real gain today. We have to tip our hats of to SiS for launching the first working 8x AGP last year, even before the omnipotent Radeon 9700 Pro had surfaced.
With games looking better than ever due to advances in programming, complexity, and APIs, the need for budget cards to support some of the latest features is critical if they're to be serious contenders for more than a few months at a time. The DFI Xabre 400 boasts full hardware support for DirectX's 8.1 Pixel Shader 1.3 specification, thereby allowing far more detailed textures to be applied to polygons, giving the impression of more life-like images. Vertex shading where the developer can design and implement an almost limitless array of special effects, though, is only supported on a software level, so the CPU has to bear the brunt of the work. Balancing hardware pixel shading and software vertex shading may prove to be a little difficult.
SiS' Pixelizer engine, a flashy term that covers the more basic functions that a present graphics card should contain such as hardware texture and lighting, various forms of mapping, full scene anti-aliasing (super sampling), put it on rough terms with the competition. The Xabre also features a 375MHz RAMDAC capable of outputting to both VGA and DVI (used in conjunction with the SiS301 chip). To gauge just how powerful the SiS Xabre 400 is from a purely numerical view, it has a 128-bit memory interface (industry standard, apart from the Radeon 9700 / Pro), a 250MHz core and 250MHz (500MHz-DDR) memory clock. A bit of simple maths gives us a total, real bandwidth of 8GB/s (128/16*500). With its 4 pixel pipelines and 250MHz core, it has 1Gigapixel/s fill rate, and courtesy of its 2 texture units per pipe, it can push out 2Gigatexels per second.
It seems quite impressive on paper, let's now have a look at the DFI card in more detail.
