Most interestingly to me, is that means OS X 10.9 is running DDR4, even though no Apple product to date that I'm aware of has shipped with anything faster than 2133MHz DDR3.
[edit for highest DRAM frequency offered by Apple]
At least until now, none of the AMD CPU can be used in Hackintosh, which is unfortunate (https://www.tonymacx86.com/).