IBM 8GB (2 x 4GB) ECC Fully Buffered DDR2 667 (PC2 5300) System Specific Memory Model 46C7420 Compatible System: Compatible With: IBM BladeCenter HS21 IBM BladeCenter HS21 1885 IBM BladeCenter HS21 1915 IBM BladeCenter HS21 8853 IBM BladeCenter HS21 XM IBM BladeCenter HS21 XM 7995 IBM System x3400 IBM System x3400 7973 IBM System x3400 7974 IBM System x3400 7975 IBM System x3400 7976 IBM System x3500 IBM System x3500 7977 IBM System x3550 IBM System x3550 7978 IBM System x3650 IBM System x3650 1914 IBM System x3650 7979