PCIe Primer - Two as one
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One of the first things that PCIe allows that hardware vendors are jumping on, is utilizing two video cards for better graphics performance. Sure, we’ve been down this road in the past, but I think the hardware gurus have finally hit on the right formula.
Anyone who’s been around the techie side of computers for the last several years has heard the acronym SLI. SLI technology is meant to allow you to bridge two video cards together. Well, it seems that along these lines, SLI changed and not everyone got the memo!
Originally, SLI stood for "Scan Line Interleave.” In this scenario, each line displayed on your monitor was given a number. Then, one of the video cards would render the even lines, while the other concentrated on the odd lines. In order to achieve this functionality, an internal ribbon cable was needed to connect the two cards inside the computer, and then an external “pass thru” cable was needed to connect the two on the outside. This technology dates back to 1998.
In 2004, NVIDIA re-introduced the term "SLI," which now stands for "Scalable Link Interface." This new technology no longer just divvies up the lines between two cards, but uses parallel processing to concentrate on the rendering details more efficiently. In this setup, the two cards actually work together as one. This configuration does NOT require the external pass-thru cable, and the two cards are connected by a small PCB internally.
In addition to SLI, another multi-card contender for the PCIe platform is called Crossfire. This is ATI’s addition to the game, hoping to compete head to head with SLI. This is a slightly newer technology (only available to consumers since September 2005), and has its pros and cons compared to SLI.
On a final note for SLI, you are now able to set up QUAD SLI configurations. Given that a board that is QUAD SLI capable, along with 4 identical video cards, adds up to quite a chunk of change, imagine the video quality and depth while playing your favorite game.
Next: Final thoughts >>
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