...I've got the i5 3570 16GBs Kingston HyperX 1600 that the board only sees as 1333....
On older (last week's
) motherboards, you often have to manually "overclock" to the memory timings. Older boards just don't reliably (if at all) handle automatically setting 1600 and above memory modules based on RAM module profiles, and I imagine that could be the case for some "new" boards as well.
I think AMD CPU using boards for example, just started handling auto-setting for DDR3-1866 and above with the 990 boards? (off the top of my head, so that may not be 100% accurate. I know for example, my ASRock 970 board defaults to DDR3-1333 with any RAM modules rated DDR3-1600 and above, so I have to manually "overclock" the RAM timings to get the 800MHz/DDR3-1600MHz actual operating speed).
Intel CPU using boards started handling these XMP/XMS/etc profiles on faster RAM modules before AMD CPU using boards. But again, I've read cases where not all Intel CPU using board manufacturers were equal.
Usually the motherboard spec shows this limitation with something like this:
Supported Memory: 800/1066/1333/1600(OC)
edit to add:
and I think Intel came out recently with yet another memory module timing profile standard, and I would guess "older" boards, even Intel CPU boards, might not be fully compatible with it.
clarify that I was talking about Intel CPU and AMD CPU using boards, and not Intel manufactured v. AMD manufactured boards.
clarified manual OC of the ASRock 970 mobo for DDR3-1600 modules