IBM PC2-5300 4GB DDR2 667MHz ECC memory module

PC2-5300 - 667 MHz The vendors who supply DIMMs to IBM stopped building PC2-4200 and PC2-3200 DIMMs in the first half of 2007. At that time, IBM qualified the usage of the newer PC2-5300 DIMMs with JS21 blades. When the PC2-5300 DIMMs are inserted into JS21 blades, the system firmware will only run the DIMMs at 533MHz, even if the PC2-5300 DIMM labels show 667 MHz. Thus, the PC2-5300 DIMMs are supported on JS21 blades.