Kingston offers "K3" kit part numbers for Triple Channel mode.
Kingston's DDR3-1333 modules automatically clock down to 1066MHz and 800MHz depending on which Intel Xeon model is installed and how many module banks are populated.
4GB DDR3-1333 Reg ECC modules come in two versions: 313/4G using x4 and 3138/4G using x8 DRAM. The two parts may be installed in the same system but not within the same memory bank. Use like modules for dual and triple channel operation.