I have been running my 1.4 @ 1602MHz (11.5x139) for the past 4-5 mths, no problems at all. I think I've reached the limit already, as it'll become a bit unstable if I add 1 more MHz to the fsb, when running Prime95. The CPU will post @ 1650MHz tho, but it won't go into windows.
I'm using my CPU...