Overheating under load?

[Earthworm]

I have a T-Bird 800 and have not overclocked it at all. When it is not under load it runs at 38-40C but when its under load it jumps up to 52-55C. I have ordered some arctic silver two and I have a pretty good HSF from 3dcool.com, it has a 35cfm fan on the HS. I'm just wondering why it jumps so much.

Oh yeah its a green core:(

Thanks

[Earthworm]

Oh yeah...
I have an Abit KT7-Raid with 384mb Crucial pc133 cl3, creative geforce ddr, sblive,
300W PS and a 20g Maxtor HD.