Product Detail 4096 Megabytes of DDR2 memory XMS2-6400 2 x 2048MB non-ECC 800MHz PC6400 240 pins unbuffered Tested at JEDEC standard latency settings (5-5-5-18) at 1.8V For 64bit OS, Quad XMS2 with DHX Technology . The "Corsair DHX 4 GB 2 X 2 GB 240-pin DDR2 800MHz Dual Channel Memory Kit" is best product for you. We recommended Corsair DHX 4 GB 2 X 2 GB 240-pin DDR2 800MHz Dual Channel Memory Kit