The Hydra Engine is a little chip that sits on the motherboard taking up only about 5W and requiring no heatsink. It lies on the PCIe bus physically, and logically between the DX or OpenGL software and the PCIe Bus driver. The software intercepts graphics calls and shunts them off to the Hydra 100 for 'magic'.

What happens really is magic. You can take up to four GPUs from the same manufacturer and put them together in a system. Got an old 2600 series ATI card on the shelf that you replaced with a 4850 recently? Why not plug it in and add a bit to performance, with the Hydra Engine, it just works.

The way the magic happens is the chip will dynamically read GPU time used, GPU memory used, textures left in GPU memory, pixel shader bandwidth and a host of other things in real time. It also dynamically figures out the capacity of each GPU in the system.

It knows if it needs to draw one million pixels a frame, and GPU1 has 3x the power of GPU2, that 750K pixels go to GPU1 and 250K go to GPU2. It can do the same for geometry and all the other functions on a sub-frame basis. Each frame, it reevaluates the mix, so if the scene changed from geometry heavy to shader heavy, it can deal with it in real time.

You can read the entire article at The Inquirer.