VR-Zone

Anything more than 2 GPUs in multi-GPU mode may sound excessive and too exotic. Not for Nvidia, as their latest driver unlocks 4-way SLI for all Geforce GTX 400 cards. This is not the first time 4 Nvidia cards have worked in tandem, however, with EVGA's Classified series motherboard and GPUs offering 4-way SLI support for the GTX 285. Curiously - GTX 400 worked fine in 4-way SLI mode on an EVGA Classified motherboard without the need for special Classified GPUs - showcasing the possibility of GTX 400 4-way SLI. This has been confirmed now as the GTX 400 series products will be compatible with any SLI motherboard with 4 PCI-e slots.

ATI have had their 4-way CrossfireX solution available since 2008 (with drivers in 2009) but it has always remained a largely impractical solution with very little adoption. Nvidia themselves have had a 3-way SLI solution. Of course, quad-GPU has always been enabled in 2 dual-GPU cards working together, but that is different from 4 separate cards.

In practice, a 4-way GTX 480 solution is likely to cost above $2000, if available, and need at least a 1500W power supply and some very serious cooling. Of course, added to all this, driver bugs and poor scaling means the 4-way multi-GPU will always remain one of those insane solutions which no logic or commonsense can justify. But they do have a market, like all things insane.

Reference: Xbitlabs