Socket F accepted Istanbul cpus just like AM2+/AM3 accepts Thuban.AMD could have opted for an F+ and make it Lisbon only compatible ,but they opted for a pin compatible C32 socket that has a new spec. for BD support. What AMD fellow engineer said in the pre- Hot Chips briefing is that the AM3 boards are not electrically compatible with BD cores due to new power management incorporated in the new uarchitecture(even though the new socket will accept the old chips).