Heh .. I have the magic potion to reveal hidden stuff on websites .. haha ..
Well, my understanding of it is that they're working together in a kind of Hybrid XFire situation but it isn't really true XFire ( if that make sense ).
DUAL GRAPHICS STUFF @ TomsHardware
.. that might give you an idea as to what to expect and how it works etc. There are probably loads of other websites out there with better ways of explaining things than I can heheh .
I'd do some research into performance with the topmost card which can be used with the CPU and then with a single VGA card and see which performs best. My guess is that you'd be better off with a single discrete VGA card in the range above the topmost compatible card for that CPU. Weigh the pros and cons and if the cost comes within a few £/$ etc, go for a more powerful single discrete VGA card ..
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