This may have been discussed before, but a quick search didn't turn up anything, which also tells me it's not a common issue. Once I go above 400 FSB, my DS3 will only run at even-numbered FSB's. Set it to 403, it runs at 402...set it to 421, it runs at 420, and so on. It's not really that big of a deal, other than having to make 16mhz jumps at a time. Possibly something I've missed causing this?