Gigaram 6GB (3x2GB) DDR3-1066 ECC DIMM for Apple Mac Pro 8-Core 2.60Ghz Intel Xeon "Nehalem" (Apple# 3 x MB981G/A) 2GB 240P PC3-8500 CL7 18c 128x8 DDR3-1066 ECC Dual Rank DIMM. This DIMM module is specifically designed and SPD configured for the "Nehelam" Mac Pro. This part will match up with 2GB modules (i.e. 3x 2GB modules or 6x 2GB modules). You cannot add a single 2GB module to 3x 1GB modules. This DIMM includes the Apple Specified Thermal EPROM Sensor. This module is compatible with the latest Apple Firmware