Well, that's going to depend totally on your cooling setup and the heatsink you're using. For instance, my XP2400 is running at 43C while cpu usage is 100% with 1.80v actual and at 10.5x212.5fsb, and runs ~39-40C. At stock voltage and stock speed, it was 35C idle. But, I have enough case airflow to make a hovercraft jealous, and a copper core heatsink with an 80mm fan that spins at ~6800-7000 rpm. With a normal cooling setup, I would think that since it's a pretty hot-running processor, ~55C at 100% load would be quite "normal".