Not true. A G41 chipset can run at a 333 MHz FSB freq (DDR2 memory clock of 667 MHz or DDR3 mem clock of 1333 MHz) without overclocking. They will not go much higher though. Upper FSB limit is about 340 - 360 MHz depending on the sample.
That is why they make such poor overclockers with CPU's with a 333 MHz FSB freq.