actually, you dont have to have your ram run that speed. those speeds just show whats the max speed of the ram the motherboard supports.
Just like if you have an 1066, and your board only support 800 max, then it will only run 800. but since in your case, its lower than the highest speed of the supports memory speed, you should run it no problem. For example, since your board supports 1200, and you have ram that run 800, then it will run 800. you dont have to adjust the timings, or at least you shouldnt.
unless its Intel, you are pretty much stuck at 667mhz of speed because of the FSB.
But for AMD, there isnt any bottleneck of ram speed because of the integrated memory controller.