After having focused on triple SLI which enables using 3 graphic cards simultaneously, we decided to come back to the subject of multi-GPU systems. This technology has now been extended to a quad-GPU configuration with both AMD and Nvidia. It’s also the occasion to publish a large report on the performances of all types of multi-GPU systems.
We won’t go over the way multi-GPU systems works which was already the subject of several articles, notably in our report devoted to
triple SLI. We will simply point out that according to manufacturers, Windows Vista facilitates the use of more than 2 GPUs via AFR mode in which each GPU calculates a distinct image. This would explain the fact that triple and quad GPU modes aren’t available in Windows XP. However, in our opinion, it’s not the only reason. We believe there was the desire to avoid too much development and support in Windows XP. In addition, AMD specifies that at the current time Windows Vista does not allow using more than 3 GPUs in AFR and DirectX 10 although Nvidia does not seem to have this problem.
A broad selection of multi-GPU solutions
Given the very large number of multi-GPU combinations and the fact that we couldn’t test them all, we had to choose the most interesting solutions.
From left to right: GeForce 8800 Ultra triple SLI, GeForce 9800 GX2 quad SLI, Radeon HD 3870 X2 quad CrossFire X.On the Nvidia side, we therefore opted for GeForce 8800 Ultra triple SLI whose advantage is its 768 MB of memory. It’s this manufacturer’s highest performance tri system even if these graphic cards are no longer in production. The GeForce 8800 GTX, which is still occasionally available at an attractive price, has similar performances. We could have opted for GeForce 9800 GTX triple SLI, but in our opinion, this card isn't too interesting. In the end, we thought it would be more informative to go with cards equipped with more memory.
For quad SLI, of course we used two GeForce 9800 GX2s, one from Point of View, the other from Twintech.
For AMD, the choice was more difficult given the flexibility of CrossFire X. All cards based on the same GPU can be mixed at will. We therefore decided to separate AMD tests into two categories. On the one hand, we tested the Radeon HD 3870 and 3870 X2 by adding a HD 3870 (triple CrossFire) and a second HD 3870 X2 (quad CrossFire) to the latter. We also tested a broader spectrum of Radeon HD 3800 combinations with particular focus on the Radeon HD 3850 256 MB combined with a Radeon HD 3870 or 3870 X2, which are equipped with 512 MB.
