It cannot handle 100c. At that temperature the metal will begin to warp slowly, and it just takes a tiny change for it to be gone. 80 is the absolute highest you want to go, 70 is safest for a stable, long life. You can usually overclock a bit with a stock cooler, it doesn't matter what you have as long as your temps are safe. Run Prime95 for 6 hours, if it does not reach 75c under full load, and does not crash or have any errors, your overclock is stable. If it has errors, increase the voltage to 1.135v and run Prime95 again. This increase in voltage WILL increase your temperatures. If it hits 80c, you will have to reduce your overclock to something cooler and more stable until you can get a better cooler. Your cooler may actually be sufficient, just not performing at its full potential due to bad ventilation, dust, or a bad application of thermal paste.