I've recently built a new computer, specs:
Asus P6TD Deluxe
Intel Core i7 920
Mushkin PC3-12800 3 x 2048 MB 8-8-8-24
WD Black Caviar 1TB
ATi Radeon HD 5850
Antec TruePower 750W
Windows 7 Professional 64bit
It's been running perfectly for almost 3 months now. Today I noticed Windows only detected 2GB RAM, I went into bios settings and restored it to default settings, thinking my overclock was the issue. When Windows booted up it did detect 6GB of RAM, but running at only 1066MHz. If I try to manually set it to 1600Mhz it only shows 2GB usable RAM, but in CPU-Z it detects all RAM sticks. After a few minutes Windows crashes with 1600MHz.
To get stability with your ram, you may have to adjust the voltage and timings manually. But if overclocking is your goal, I suggest you leave the ram at 1066 and let the board use whatever ratios are built in as you increase the cpu fsb and slowly increase the ram voltage. I personally won't run ddr3 higher than 1.65 unless the manufacturer recommends a higher setting.
Foladko we got it I would follow o1die's advice. Why are you worrying about what it used to do just look at what it's doing now. In any case raising speed of the RAM to 1600MHz will provide you with negligible real word benefits at best.