Well, after you remove the case, you will have to be damn careful and remove the clips that hold the heatplate on,. Then just wipe off the core, and you will see what it is.
I have done many of them, and found the best way to remove the clips is to take a small pair of wire cutters wth a spring loaded handle, place the tip of the cutters right between the top of the tab on the clip and retaining post, and squeeze. It will not cut the clip, just separate the tab from the post easier than any other method I have used, and is much less likely to damage the PCB than a slipped screwdriver or prying with needlenose pliers could.
EDIT: Keep the Athlon flat on a bench or table when doing this, and when the first clip comes off, make sure that you lightly push the partially removed PCB down so the core remains flat against the heatplate, and does not rock around while removing the 2nd clip to prevent chipping the core.