RAM & Memory Upgrades
8GB (2 x 4GB) DDR2 800MHz PC2-6400 240-PIN ECC FULLY BUFFERED (FBDIMM) MEMORY RAM KIT COMPATIBLE WITH MAC PRO (EARLY 2008)
SIZE/CAPACITY: 8GB KIT (2 x4GB) VOLTAGE/POWER CONSUMPTION: 1.8v CAS LATENCY: CL6 SPEED: PC2-6400 (800MHz) TYPE/INTERFACE: 240-PIN DDR2 ECC FULLY BUFFERED DIMM (FBDIMM) - APPROVED 240-PIN MAC PRO DDR2 ECC FULLY BUFFERED DIMM KIT
https://www.bizrate.co.uk/ram_memoryupgrades/8gb-2-x-4gb-ddr2-oid1709108940.html