Product Detail to use fully buffered DIMMs, your server or motherboard must use FBDIMM architecture. An FBDIMM will not fit into a standard DDR2 socket, and a DDR2 module will not fit into an FBDIMM socket . The "Crucial CT2KIT51272AF667 PC2-5300 CL 5 Fully Buffered ECC DDR2-667 1.8V 512Meg x 72 4GB X 2 8GB Kit" is best product for you. We recommended Crucial CT2KIT51272AF667 PC2-5300 CL 5 Fully Buffered ECC DDR2-667 1.8V 512Meg x 72 4GB X 2 8GB Kit