|There are two CPU:DRAM frequency ratios that offer best performance for an Intel system...1:1 or 1:2. The word "frequency" is very important. Do NOT work with the bogus advertised ratings. An Intel 800MHz FSB CPU does NOT run at 800MHz, it runs at 200MHz frequency. And DDR2-800 does NOT run at 800MHz, it runs at 400MHz frequency.|
Your CPU runs at 200MHz frequency by default. For 1:1 ratio, the RAM would need to run at 200MHz. That would mean underclocking the DDR2-800 to DDR2-400 speed. For 1:2 ratio, the DDR2-800 would need to run at 400MHz, which it already does by default.
DDR2-1066 runs at 533MHz...that doesn't fit either the 1:1 or 1:2 ratio criteria so peformance will be less than optimal unless you overclock the CPU. And the two choices in CPU frequency would be 266MHz (for 1:2) or 533MHz (for 1:1). It's doubtful that your board can handle 533MHz frequency (2133MHz FSB) but there are options in between.
The bottomline is that if you want to overclock your CPU, you do NOT need DDR2-1066 RAM, you'd just be wasting your money. Just keep the DDR2-800, jack up the CPU frequency to 400MHz (1600MHz FSB), lower the CPU multiplier to say, 8x, adjust the RAM settings so it stays in sync at 400MHz...this will run the CPU at 3.2GHz. If you're experienced at overclocking, you know that there are numerous other settings that will also need tweaking to be able to pull it off.