I have 3 sticks of 4G, and 2 sticks of 2G FBDIMMs, all same manufacturer timing etc. I have not been able to install these in such a way that I see 16GB in the BIOS screen. I always see 12 GB with some disabled. I have tested them by swapping, and all are physically OK.
What is the best way to install these five sticks?
The part numbers of teh DIMMs would help
The TPS http://www.intel.com/support/motherboards/server/s5000psl/sb/CS-022619.htm list the dimm popultion information
It is recommend to use all the same type DIMMs, but basicly you should be good with first 3 blue slots with the 4g DIMS and the last blue and black slot with your 2g dimms. As long as your not mixing dual and quad rank dimms this should work.