ATI CrossFire

With scores like that it’s clear that you should be able to push the resolution envelope with a CrossFire system, just like you can with a high-end SLi machine, so you’re probably wondering why I capped the testing at 1,600 x 1,200. The simple answer is that I didn’t cap the resolution, ATI did. It seems that not only is the CrossFire method of connecting up the two graphics cards not quite as elegant as the SLi method, it also brings with it a resolution ceiling.

Because the two graphics cards are connected via a DVI port, the resolution that CrossFire can support is capped by the upper limit of a single link DVI connector. A single link DVI port can output a maximum resolution of 1,600 x 1,200 or 1,920 x 1,200 with reduced blanking employed. So, the highest resolution available to a dual GPU CrossFire system right now is 1,920 x 1,200 if you happen to have a 23 or 24in widescreen TFT. But for most gamers that don’t have over a thousand pounds to spend on a screen, 1,600 x 1,200 is the best you’re going to get.

The most bizarre thing about this situation is that a single Radeon X850 XT can produce playable frame rates above 1,600 x 1,200, but then if you add a second card that luxury is off the menu. This resolution limitation is a major problem for CrossFire as it stands today, but it shouldn’t be an issue in a few weeks. Why? Because that’s when we should see ATI’s next generation of graphics cards, based on the new R520 core.

The R520 boards will feature dual link DVI connections, which means that the resolution limitation issue seen in the R4xx boards will be a thing of the past. With this in mind, an R520 based CrossFire system should be able to reach dizzying resolution heights, although I’ll have to wait until I get my hands on the hardware for conclusive results.

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