Wednesday, September 05, 2001

Introduction

Once upon a time, in a land not so far away, manufacturers presented users with a range of video cards that were based on an equally wide array of graphics chips. Today however, the market is increasingly dominated by Nvidia, which has successfully managed to bankrupt, or take-over most of its competition. Its because of this increasing homogeneity in the marketplace that we're quite pleased to present you with our review of a vid-card based on STmicroelectronics' Kyro II.

The 3D Prophet 4500 is the fruit of the union of three separate enterprises - Hercules, STmicroelectronics, and Imagination Technologies. The first step in its conception came about at Imagination Technologies, which developed the TBR (Tile-Based Rendering) scheme that's at the heart of the Kyro II. The next stage in the Kyro II's development was then in the hands of STmicroelectronics, which manufacturers the PowerVR Series graphics chips which implements the TBR system. Finally, because STmicroelectronics, as well as Nvidia for that matter, isn't in the habit of selling the finished product (in this case, the graphics card itself), it was up to Hercules to put together the final product.

The technology behind the Kyro II

Conventional graphics cards typically need to render a good deal of superfluous data when drawing a scene. This is because they end up calculating information dealing with objects that aren't actually visible from within the user's line-of-sight. Once these calculations are completed, Z-Buffering is used to determine what's visible, and what isn't. This method has its drawbacks though, as it requires a great deal of number crunching and memory bandwidth, simply because all of the scenery is drawn whether or not certain parts are actually visible.

The Kyro II doesn't do things the same way however, thanks in no small part to its TBR technology. Whereas most graphics cards render draw all objects as if they were composed as a series of triangles clustered into polygons, the Kyro II prefers to deal in tiles. The use of this tile-based rendering format allows special registers to be implemented, which determine which are visible.

This method allows the Kyro II to save an enormous amount of memory bandwidth. Normally, Z-Buffering calculations can only be done once the entire scene has been written to memory. With the Kyro II, the calculations have been done before the data has been written into RAM. In simple terms, the Kyro II only objects that can actually be seen are rendered and written into memory, where they are handled by Z-Buffering.

The beauty of this technology is that it can be applied to any game without the need to apply software patches. What's more, because the Kyro II has a greatly reduced need for bandwidth, DDR memory isn't required - which reduces its overall cost. Finally, because those pixels that are destined to be written to screen are handled internally in 32-bit color, if users choose to work in 16-bit color mode, the conversion will be handled internally by the chipset, thus providing more vivid-colour than obtained by many competing cards. Basically, the Kyro II gives users a real incentive to work in true 32-bit color; after all, its already been calculated that way!

Next: Specifications