Sources close to ATI Technologies said the company was preparing a technology that is similar to NVIDIA’s Multi-GPU Scalable Link Interface, but offers additional flexibility and enhancements not presently available on NVIDIA’s approach to graphics multiprocessing.

The multi-GPU technology from ATI will presumably be branded as Multi Rendering and will have a number of fundamental shifts from technologies of this kind, sources said. The main thing ATI is currently working on is how to enable two different graphics cards to work in pair, providing enhancements to gamers who use the technology. NVIDIA’s SLI technology only allows two very similar graphics cards to work in parallel, which puts some restrictions with deployment of multi-GPU graphics sub-systems by end-users. It is unclear whether there are any other advantages ATI’s Multi Rendering technology may offer in addition to higher average framerate.

Timeframe when ATI Technologies is likely to offer its Multi Rendering is unclear. NVIDIA said its SLI is a complex of hardware, GPU and core-logic products, and software, ForceWare drivers, technologies. It is unclear whether ATI has chipsets that sports special logic to allow Multi-VPU operation inside, but it known that all ATI’s graphics processing units are able to work in parallel, as the company supplies them to companies like E&S for high-end graphics systems.

NVIDIA’s SLI is a technology that enables two NVIDIA-based graphics cards to operate in a single workstation or PC delivering higher graphics horsepower. A special mainboard with two PCI Express x16 is required for such configuration. According to NVIDIA’s estimates, typical performance advantage dual NVIDIA GeForce 6800 Ultra bring is about 75% - 80% when operating on a system running NVIDIA nForce4 SLI chipset that boasts special enhancements for Multi-GPU technology. NVIDIA’s approach requires special circuitry to be incorporated into GPUs and, for extra speed gain, into core-logic. Alienware’s Video Array technology does not require any special logic to be incorporated into graphics or system chips.

Officials from ATI did not comment on the story.