I'm not 100% sure what the actual safe limits are (AMD says that they are okay up to 75C or so, but I would never let them get near that). My 1.4ghz T-bird used to hit 61C at times in the summer with the stock cooling and generic thermal goop before I bought a new heatsink, fan, and TherMagic. As long as it doesn't crack 60C or so, you should be okay, but if it gets any higher than that, consider buying a new heatsink. I ended up with an AX-7 and a low-RPM 80mm fan, and my rig now runs 44C full load, when I have it overclocked to 1553mhz, it runs at about 48C full load. So it does the job well.