Memory Speed and motherboard/CPU compatability

Hi Toms Hardware
So I thought I had found the memory for my new Gaming build, but Ive seen a lot of posts here on Toms Hardware about new builds that have made me uncertain.
Ive chosen the Asus Crosshair IV Formula ( ) as my mobo, and the AMD Phenom II x4 955 ( ) as my CPU and then the memory. I checked the Mobo and CPU specs and found that the highest memory speed compatible was DDR3 PC3-10600 1333MHz and so I chose this memory: - Datasheet from :
But now ive seen a lot of posts with people wanting to use PC3-12800 1600MHz and even PC3-16000 2000MHz memory with their AMD 890FX chipset and Phenom II CPUs. But the mobo specs says that it only supports memory of that speed when its OC'd and the CPU spec doesnt say it supports those speeds at all.
So my question is, will I benefit from the extra memory speed when my mobo/cpu allegedly doesnt support those speeds, or will my mobo automatically reduce the speed to maximum supported, or will I actually get poorer performance ? Im asking because noone in the new build threads have pointed out the high memory speed, so I got confused.
And another thing, would I be able to buy the memory with higher speed and then underclock them to the supported max speed and lower timings instead to get better performance? because I think I saw somewhere that AMD CPU overall system performance benefits more from lower memory timings rather than higher clock speeds ?

edit: In case I will benefit from higher speeds than PC3-10600, could you recommend some memory modules ? preferably mushkin, corsair or kingston as those are the quality brands available in my country. also, im gonna install a Zalman CNPS 10x Extreme CPU cooler, and memory modules taller than 36mm wont fit because the heatsink blocks some of the memory slots. Although, if you can recommend another CPU Cooler that will make me fit memory modules taller than 36mm that increases my performance noticeably (the momory modules increasing performance, not the cooler), and will cool better or as good as the Zalman, that would be appreciated aswell.

thank you for reading
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More about memory speed motherboard compatability
  1. Some clever mind must know this for sure
  2. I have seen plenty AMD DDR3 1600 8/8/8 or 7/7/7.
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