Interesting. I got the information from one of our hardware folks and he said 175F was the beginning stages of silicon degradation. Perhaps melting was a bit extreme. My chip does have signs of degradation though and it has only ever reached 90C or so. I have small halos in the brown material surrounding the entire CPU and it's various chips on my AMD 3200 XP+. My XP 3200+ has about 6 chips arranged 3x3 around the central chip that is raised up a bit. When you look parallel to a light source you can definitely see some surface alterations in areas where heat has built up.
Sorry, but silicon doesn't melt for several hundred degrees above 175'F. Having worked at the site that handles "faulty processor returns" at AMD in Europe, I have seen a few examples of what happens when the processor gets FAR too hot - the common problem with these processors is shorts between pins - this is caused by the solder that is used to connect the actual chip to the substrate melts - this happens at around 200'C - roughly 400'F.
Athlon 64 processors all have an internal shutdown temperature sensor that shuts the processor off before it takes any damage. This will probably happen around 100-120'C.