Burned up my 3870 video card and wanted to replace with the cost efficient 6850. My motherboard is a k9a2cf and has a 2.0 slot. All the new cards are 2.1. Is this a problem. I googled several times to no real answers. Messaged MSI but awaiting a conservative answer along the lines of "the board was not made when the cards came out" type of reply. Thanx in advance for any help.
So, MSI wrote and told me that it would be better if I did not use a 2.1 card.
You'll be fine.
The fact is there are no motherboards has a PCI-e 2.1 slot. Therefore, if a PCI-e 2.1 card does not work with a PCI-e 2.0 slot, then AMD will be loosing a lot of money since all Radeon HD 6xxx cards are PCI-e 2.1 cards.
Just try not to stick a PCI-e 2.1 card in a PCI-e 1.x slot. There maybe some compatibility issues unless the motherboard manufacturer released a BIOS update to fix the potential issue.