Hi guys I had previously decided to sell my 5870 and go with a new 580 gtx. However, I'm not having the greatest luck with my craigslist posting and would rather not use ebay. I'm willing to just go with a 5870 for a while but as I'm seeing prices plummet on first gen dx11 cards, would I see a significant gain from adding a 5970 to the mix? I figure the price will continue to drop once the new dual gpu cards arrive and maybe I'll be able to grab one for sub 400$ within a few months. The only issue I have is how the 8x8 limitation on my mobo will relate to real world gaming performance. Will the 5970 act as one gpu? I'm currently working&going to school full time and would rather not just "throw away" my 5870. Thanks i5 email@example.com, 5870 1 gb, p55pro 1080p
I'd go with dual 5870's rather than adding a 5970. A lot of the time, trifire doesn't help much if at all. It'll save you some money too. x4 performance in crossfire with a 5870 on the p55 boards can cause about 30% loss in performance.
The 5970 is two GPU's. Each GPU on the card has it's own memory. The only difference between two 5870's and a single 5970 is the 5970 shares the PCIe slot and has lower stock clock settings, partly due to heat issues.