Recently bought a second 4890 for CF and didn't realize this, but apparently the standard CF bridge is too short for my cards to be any decent length apart from each other. They are both on PCI2.0@16 but extremely close together, less than an inch apart. I'm currently playing BF3, with both GPU's fans on 100%. The first card has gone up to 105c. Since then, I've upgraded some case fans and now the max it goes up to is 95c. The second card is fine, like 70c under load. Is 95 too hot you think? If I invest in a longer CF bridge I will have to place a card in a PCIE2.0@8x slot. Will this decrease performance?
Also, I must say, I'm getting great performance in bf3 at 1080p with all settings on ultra. I'm getting a steady 60fps on some maps, other 40-60fps. 4890s are def still a force to be reckoned with.
I have a 120mm fan right on the side blowing air directly at both GPU's. I also have an additional bottom 60mm fan blowing air upwards at them as well. With this setup, the first card still reaches 95c. For now, I have opened the case up and set up a powerful(non-pc, regular) fan blowing directly at the gpus. Now the first doesn't go above 70c. This is only temporary though.
95c is fairly hot and would benefit from extra cooling if you can supply it eg more fans or ramp up current fan speeds using catalyst or afterburner (afterburner has user defined fan speed for different temps)
the 8x slot wont make too much of a difference to your performance and should give better air flow to the cards