DDR3-1600 Corsair XMS3 RAM, ASUS SysInfo util says 667MHz?

[jmichae3]

I have an ASUS P9x79 deluxe and i7-3970x and Corsair XMS3 CMX32GX3M4A1600C11 memory (2 4x8GiB Sets for total of 64GiB, size is not the issue here nor is the mobo or proc I should think)

why does MaxBandwidth show as 667MHz? isn't this supposed to be 800MHz according to wikipedia on their DDR3 article?
SPD it's supposed to be 1333MHz (667MHz) but tested speed is 1600MHz (800MHz).
so, why is the SPD (whatever that is) different than the actual speed, and what really is the speed if the asus sysinfo is reporting 667MHz?

wikipedia article:
http://en.wikipedia.org/wiki/DDR3_SDRAM
memory is
http://www.corsair.com/en/memory-by-product-family/xms-classic/xms3-32gb-dual-channel-ddr3-memory-kit-cmx32gx3m4a1600c11.html

I don't understand why also the tested speed spec on the RAM says 1600MHz but the SPD spec on the RAM says 1333MHz. so I am a little confused here.

 

[logang]

a lot of times you need to manually set RAM speeds above 1333 in the bios. That may be what is causing your issue.

 

[Alin Prema]

By default, they are running @ 1333MHz. You have to enable Xtreme Memory Profile (XMP) in BIOS in order to run @ 1600MHz.