The integrated memory controllers on the Phenom II's operates at 1333MHz. They do NOT support 1600MHz DDR3 Dimms.
Except they do. Kind of. When you set the memory speed higher you overclock the memory controller. Most can make it to 1600MHz, but they aren't guaranteed to. When i had this problem mine stopped a little short, i think 1580. The recommended way to do this is to set the FSB to 240, up from the default of 200, instead of trying to set the memory speed in the bios. Then turn down your CPU multiplier if you don't want to overclock.
Please see below, this is for GSkill but the issue is with the CPU not the memory, and it should work for you as well, once i did this i was able to tighten my timings down manually.http://www.gskill.us/forum/showthread.php?t=7688