There is no "safe limit" on FSB, if you put it too high, it will not boot - simple as that. Voltage on the other hand is a whole different story. You NEED to increase Vcore and northbridge voltage to get any kind of half decent overclock (yes, I know people run under VID overclocks for the epeen - dont flame). Vcore should ideally never get over 1.4v. Some people say 1.362 is the max, some say 1.5. It all depends on how long you want your chip to live for and how well it is cooled. Northbridge voltage can be safelt set to 1.4v and it will drastically help the overclock. RAM voltage can also be upped - what brand and speed RAM do you have?