I know there are other threads that cover this, but it seems like clear answers haven't exactly been given regarding the latest adapters...
If the adapter is not specifically labeled as Active, and it does not have an extra USB cable to provide power, the odds are it is passive. I tried a generic one like this when I couldn't find something specifically labelled as active at my local shops. What you will see is that your CCC shows three monitors connected, but you can only run 2 at a time. It will be impossible to setup a three monitor eyefinity group.
When you have an actual active adapter, you will see three monitors in CCC again, but you can actually expand your desktop or clone to all three at the same time, no issues. You will also be able to setup an eyefinity group as well with no issues.
The cheapest ACTIVE adapter I found locally was the XFX one. No USB needed, just a display port, short cable (4" or so) and DVI port. Max res is 1900x1200 with this type. If you need a higher res, you will need one of the expensive usb powered active adapters. Example usage would be for running dual-link DVI monitors like 30" 2560x1600 beasts... If you can afford multiple ones of those, you can afford the better adapter. :)
NewEgg has a few to choose from in the $25 - $39 range. Saphire has some without USB now, as well as some other off-brand companies. Even more helpful, some are actually stating on their packaging if they are eyefinity compatible. In most cases, they appear to be correct. :)
Anyway, my testing was done with 5870's going to DVI only monitors. I'm about to test one more variable when I hook up my 5970 in eyefinity mode. I need a mini-displayport to regular displayport, then my active dp adapter to go to my DVI connection. Wish me luck... ;)
Edited by GrJohnso - 12/9/11 at 4:54pm