I switched out my phenom x2 555 BE for a Athlon x4 640.
It's multiplier locked so the only way to overclock is FSB
I pushed the FSB to 220 giving me a 300mhz boost. Everything is stable. Temps are fine too, I have one of these massive heatsinks and fans.
I didn't change any else though, seems to be running fine at these voltages but...
the HT Link speed & North Bridge is at 2200mhz and my 1333mhz value RAM is running at 1466mhz
Is it safe to keep it running at this level in the long run?