* Ganged – single dual channel mode for RAM. All cores get full time access to 100% of the ram. 1×128 bit

* Unganged – dual single channel mode for RAM. Each core at one time gets access to a stick of ram. 2×64 bit

So unganged is theoretically faster as each core gets its own memory access. Nvidia calls this “Locked vs unlocked” architecture.

AM2+ support for one DIMM per channel at 1066 means 2 sticks need to be put into 2 memory channels (one channel is usually on the adjacent DIMM slots ) to make them operate at 1066, not 800 speed (the performance gain might be minimal though).