Yesterday I took the HS/Fans off of my two XP 1600's to make some changes. In examining my Thaisol HS's, after cleaning off the Arctic Silver, I noticed the cpu cores actually "engraved" the copper on the bottom of the HS. I could almost read mirror images of the stepping/serial # and stuff from the top of the core in the copper bottom of the HS. I've never seen this before. Is the HS putting too much pressure on the core? I don't want them to crack. I reinstalled them and performance is normal.