User Manual
Page 30
... memory module in any slot as a DDR2 DIMM but is notched differently to prevent installation on a DDR2 DIMM socket. A DDR3 module has the same physical dimensions as a single-channel operation. DDR3 modules are developed for better performance with four Double Data Rate 3 (DDR3) Dual Inline Memory Modules (DIMM) sockets.
... memory module in any slot as a DDR2 DIMM but is notched differently to prevent installation on a DDR2 DIMM socket. A DDR3 module has the same physical dimensions as a single-channel operation. DDR3 modules are developed for better performance with four Double Data Rate 3 (DDR3) Dual Inline Memory Modules (DIMM) sockets.