Crossfire or Single?

[Kasm]

I already have a 4850 512mb card. Would it be more cost effecting to buy another 4850 or buy a 5000 series card? Also, which will perform better?
I will be using this pc at a resolution of 1920x1080.

Also, any motherboard with 2 8x lanes will do crossfire, right? or what do I need to look for specifically?

[GotNoRice]

A 4850x2 will perform comparably to a 5850, however 4850x2's have 1gb per GPU. Having only 512mb will hurt it a bit at higher resolutions. At 1920x1080 you will probably be okay unless you really crank the AA.

The main reason you would get another 4850 is the cost. That is a lot of performance for only having to buy one additional cheap card. You are talking about possibly 1/3rd the cost of getting a 5850... If cost is not an issue then just get a single card.

[freakdiablo]

You may have to check specifically if your motherboard supports it.

GotNoRice pretty has the major points. What it comes down to is are you willing to spend more for a 5850 (that is if your motherboard is xfire ready and you have a powersupply that is up to the task).

[4GHZ_or_bust]

DOn't forget power supply. Some may not like having 2 video card, and 5850 would draw a lot less than a pair of 4850.

[Catscratch]

You might wanna check the link here:
http://www.overclockers.com/forums/showpost.php?p=6422757&postcount=12

[bda1967]

5850's are getting harder to find. At least the $300 ones are.