Quote Originally Posted by saaya View Post
silverstone had a quad 9800gx2 gpgpu demo at computex and they said it scaled linearly with every card they added... which means pciE bandwidth wasnt an issue at all as adding more cards results in some slots switching from 16x to 8x...
I'm not so sure about that.

There are multiple constraints, and bandwidth is just one. #GPUs has to be >= #frames being rendered ahead. Hypothetically, if you had 100 GPUs running at 50fps, those 100 frames would be 2 sec of lag. And D3D and OpenGL have limitations on #chain/buffers.

There is also diminishing returns due to cost of partitioning work, and how uniform the work units are. Most games I play dont have exact same pixel/texture/vertex workload on all parts of the screen all the time.

Bottom line:
If you cant get anywhere near 50% let alone 100% scaling in many (not all) games with just 2 GPU, how do expect it to be possible for quad?