I just got a mobo that is crossfire capable, I already have a 1gb ati hd5670 and plan to get a second one to crossfire in a budget gaming system, should I get another 1gb or 512 mb? do they both need to be 1gb for optimum performance?
What resolution do you run at? If its 1920x1080 or higher 1GB will provide a few FPS better, if its less then it doesnt matter as memory wont be a limiting factor, but i would still suggest getting the full 1GB as it means that you get the max potential out of your CF setup and dont end up limiting one of the cards.
okay thanks everyone for the info, now what if I crossfire a 5670 with a 5770 first will that work,and second will there be any benifit over the 5670 crossfire setup?, also does aa mean anti aliasing? and whats af, forgive my ignorance I've mainly been a console gamer!!
Or buy a single 5850, which is equal to or cheaper than 2 5770's, and also leaves you the option to add a 2nd 5850 should you ever decide you need more performance later.
As has been stated, matching the amount of memory in CrossFire configs ensures all the memory of both cards will be used. More memory is useful in a few game titles regardless of the resolution, and in most games at higher resolutions. More memory can also allow "eye-candy" such as Anti-Aliasing to be enabled without significant performance loss.
Single cards are easier to trouble shoot if/when you get problems, run cooler and use less power. As long as your power supply is of a good quality you should be able to crossfire a pair of 5670's, but your probably better going for a single card solution. Save a bit more and get a 5850.