Integral IN3T2GNYNGI 2GB DDR3-1066MHz PC3-8500U Memory RAM
A-Tech 4GB (2 x 2GB) RAM for HP Compaq 4000 Pro & 6000 Pro - (Small Form Factor & Microtower) - DDR3 1066MHz PC3-8500 Non-ECC DIMM Memory Upgrade Kit at Amazon.com
OWC 2GB PC8500 DDR3 ECC 1066MHz DIMM Memory Compatible with Mac Pro & Xserve 'Nehalem' & 'Westmere' Models (OWC8566D3ECC2GB) at Amazon.com