Nvidia's SLI technology:
SLI, which is short for Scalable Link Interface, was introduced by Nvidia when the first PCIe motherboards hit the retail market. Well, introduced is a big word, as the SLI principles were already known to the big public as Scan-Line Interleave which was develloped by 3Dfx (which was later acquired by Nvidia) to support multiple graphics cards producing a single output. In other words, you place more than one videocard in your computer and all those videocards co-operate to render one output signal, faster than when you'd do the same with one videocard.
Nvidia has done some changes in the design of SLI, going from "you need to identical videocards" to "you need to same type of videocard". They also introduced the Tri-way SLI solutions and even Quad SLI, which places four gpu's in one system, wasn't left out. The main problem, however, is scalability. Nvidia claims to have excellent performance scaling technology, but in real-life applications, adding another videocard doesn't always pay off. Most of the time, you have an increase in FPS of about 35-50%, because when adding an extra videocard, you need a processor that is capable of handling all the information sent by your graphics processing units. However, in the low-end cards segment, this SLI technology story is really interesting, because the CPU doesn't have to be thát good to handle the extra VGA power.
We have released two other articles concerning the SLI technology, if you're interested, please have a read.
Talking about SLI, we tested two Leadtek 9600GT Extreme samples and compared the results with the 9800GTX reference board. Performance wise you can easily judge that SLI can give you quite some extra performance, up to roughly 70% increased FPS! Here and there you'll stumble upon games which have less support for NVIDIA's multi GPU-technology, there you'll have to do it with around 30% extra performance. But on the other hand, even with the 9800GTX having only one GPU and thus probable less configuration problems, the card never took the lead in average frame rate over the dual 9600GT's branded Leadtek. Yet, again, in CM DIRT for example, the GT's had to deal with the phenomena called Micro Stuttering, this does not occur when using single GPU configurations.
~ Leadtek 9600 GT SLI reviewed and compared with 9800 GTX.
NVIDIA Geforce 9500 GT
A few words on SLI. I cannot deny nVidia's SLI, while exciting at first is now thought of as a marketing gimmick which seduces the Gamer or PC-Enthusiast into spending twice the amount of money for two cards which produce twice the heat, require twice the power and take up twice the real-estate. The choice to release QUAD SLI updates in the future seems 4x as silly. The founders of 3DfX are more than likely rolling over in the proverbial 3Dfx grave, excavated while trying to integrate multi-GPU technology onto a single PCB. SLI reborn as Scalable Link Architecture IMHO probably coined the internal marketing phrase Profiting off the passion. Sadly we see this occurring throughout the PC-Industry. While I do respect Asus without whom there may be no "Enthusiast" since they were the pioneers of OEM, they are in the end a for profit enterprise.
~ Asus Extreme N6600GT Review - SLI on a Budget.
The cards we used for this SLI follow-up article are the Leadtek and Galaxy we already tested in our previous 9500 GT article
. We had no issues placing them next to each other in an SLI configuration, although both cards have a different bios with different clock frequencies and even have different revisions of the gpu core.
Both of these 9500 GT's perform well enough in my eyes. They're low-end and thus by definition not breaking and performance records. As both cards were released on day 1 of the official release, the prices are a bit high for low-end cards, especially when you compare against their DDR2 brothers and sisters. However, these prices will certainly drop and with the 55nm version coming, I cannot say these are not worth to consider. The last part of that sentence is important ... 'worth to consider' ... there are a lot of different products on the market and most of them are pretty much equal in terms of price/performance ratio. Some are better; some are cheaper and in the end it all depends on what card you feel is best for you. In the low-end segments, there is nothing like THE best card, there are a lot of possibilities. My advice, in other words, is that you should at least consider the 9500 GT when buying a low-end card.