VIA's K8T900 Chipset
S3's approach to multi-GPU support is to handle the process through drivers rather than with proprietary hardware or cables, in the same way NVIDIA does it with low-end GeForce 6600's and ATI does with the X1300 and X1600. With S3's new S27 Chrome graphics cards, two cards can be installed and a special driver is all that is needed to combine GPU processing. This approach not only avoids bridge clips or cables, it also enables the technology to be open platform, free to function on multiple chipsets supporting two PEG slots. The only catch at this point is that MultiChrome only works with two S27 Chrome graphics cards, although it's a safe bet more models will support MultiChrome in the future.
Essentially, S3 crafted MultiChrome drivers that split the video processing equally between two S27 Chrome graphics cards using two methods. The first is Split Frame Rendering which does as its name implies, splits a single frame so each card processes half of a frame. The next method is Alternative Frame Rendering which sends one frame to one S27 Chrome card while the next frame is delivered to the other one. Below is a grid showing what performance increases we should expect with a MultiChrome Configuration.
The performance increases are represented in percentages rather than FPS and show a wide range of variation. Compared to a SLI or Crossfire set up, MultiChrome appears to work better with some games than others. Keep in mind, though, that the Chrome 27 is an affordable card not intended to compete with high-end graphics cards as we are used to seeing.