Oh, yeah, my bad. I read that DDR3 SDRAM allows DRAM chips DRAM chip capacities of up to 8 gigabits (Gbit). I forgot to do the calculations. Since there are up to four ranks of 64 bits, that maximum capacity is 16 gigabytes.
But according to Wikipedia, Intel CPUs had problems addressing beyond 8. This problem was fixed in 2013. I guess a firmware update has done it.