4GB 2 X 2GB PC2-5300F 667MHz 240 pin DDR2 SDRAM ECC Fully Buffered FB DIMM Server Low Power Memory for HP Workstation XW8600 (PARTS-QUICK BRAND). Equivalent to HP Part Numbers: 397413-B21, 442823-B21,
Crucial 4GB DDR2-667MHz (PC2-5300) CL5 ECC RDIMM DR 240-pin Server Memory CT51272AB667 at Amazon.com