But the main question is whether it actually is required with 2 CPU's in order to use 2 8 GB modules on the mainboard ?
Answer : No
3.2.1 Processor Population Rules
You must populate processors in sequential order. Therefore, you must populate Processor socket 1 (CPU 1) before processor socket 2 (CPU 2).
When only one processor is installed, it must be in the socket labeled CPU1, which is located near the rear edge of the server board. When a single processor is installed, no terminator is required in the second processor socket.
For optimum performance, when two processors are installed, both must be the identical revision and have the same core voltage and Intel
® QPI/core speed.
Processor sockets are self-contained and autonomous. However, all configurations in the BIOS setup, such as RAS, Error Management, and so forth, are applied commonly across sockets.
HOWEVER, the only DIMMS a single CPU will be able to access are the DIMM in slots A - C (6 DIMMS)
Any memory placed in D-F will not be reconized.
Always use DIMMs off the tested memory list to avoid problems.