I have this chip programer already. I used it to flash my titon ridge thunderbolt card.Hmm, doen't it have to be at least UEFI and not legacy bios?
If you have access to the chip (meaning you went trough the mess of removing this monster of a carbon glued cooler of the 6800/6900/xt), also a USB-hardware programmer like the well known and cheap CH341A will do. The chip does not have to be desoldered to get it programmed!