Pardon my ignorance but 5830's as far as i know can only run in a dual setup for ~530 mhash
Would be keen on 5850's ??
You don't need crossfire to mine so you can run as many as you want on riser cables.
The 5850 is a better card (more efficient per Mh) but will cost you at least 25% more than a 5830.
If electricity is cheap/free, think of that as buy 4 get 1 free.
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