What's under the P4 478 IHS ?

[Snubben]

I'm curious on what lies beneath the 478 P4 integrated heat spreader (IHS).
Is it just a small die like on the P3 or is it a larger one like the 423?
If anyone has any tech info on the P4 die and IHS (the thermal conductivity between them, the contact area and so on) please let me know.

[stymee]

This might help a little....

http://www.overclockers.com/articles486/

[Yodums]

The die is a little bigger than the P3.