Nvidia SLi (Scalable Link interface) dual graphics cards review.

What with the earlier release of the Alienware and their dual-graphics card system Nvidia now show off their SLi technology dual graphics cards system using the same name from the earlier 3dfx dual graphics card technology but uses the new PCI Express interface. Nvidia bought 3dfx with all its patents a few years back now.

Nvidia is using its NV40 core GeForce 6800 graphics card with an additional gold connector at the top to interconnect two cards with SLi.

Obviously you need a motherboard with two dedicated PCI Express x16 slots and two special Nvidia GeForce 6800 graphics cards which are interconnected with a special Nvidia SLi PCB which has a very high bandwidth capability as it has to carry all communication needed by the graphics cards.

One Nvidia graphics card acts as the video master while the other is the slave.

All Nvidia PCI-E graphics cards are likely to be capable of running in SLi setup including the Quadro series of graphics cards.

The 3dfx SLI technology rendered even scan lines on one card and odd scan lines on the other. The output was then combined to produce the single signal going to the monitor.

Nvidia SLi divides the scene to be rendered based on giving each graphics card 50% of the work to do so that each card takes the same amount of time to process the amount of scene it is given by the controlling Nvidia SLi software. As shown in this diagram it does not mean half the scene to be rendered.

The finished rendered data is then sent over the Nvidia SLi interface from the slave GPU to the master GPU for composing into the final scan to be outputed to the monitor.

Alienware splits the scene horizontally in the middle and gives one card the top half and the other card the bottom half of the scene to be rendered. The output from each graphics card then goes to an additional card where the signals are combined and outputed to the monitor.

Nvidia SLi thoughts.
Good to see the new possibilities of the higher bandwidth of the PCI Express bus are being used to run two graphics cards as one. But at what price.

Specialized motherboards with at least two dedicated PCI Express x16 slots and not a mish-mash and of course two special Nvidia SLi graphics cards capable of working together. Very expensive and not expected until some time towards the end of the year. But what sort of performance increase could you expect for all this cost. At least 1.85 increase to make it worth the financial outlay.

If you are looking at buying should Nvidia market its lower performance graphics cards with this Nvidia SLi ability you would have to balance the cost compared to simply investing in a high-performance single graphics card. So as you weigh all the things up you end up only thinking of Nvidia SLi dual graphics cards as the top, top of the range only.

Not a system for us everyday ordinary Joes & Janes for office or home use tapping away writing a letter to auntie Flow in Australia.

But that said. This is an excellent idea by Nvidia as every little technology improvement pushes the performance and quality of graphics cards to even higher levels. We all know that in the future when decent large sized flat monitors running very high resolutions of whatever technology are available at a decent price people will also need the much greater performance that dual graphics card systems offer. A few years to go yet, we thinks.