For what its worth, I have kpt hold of my P4... A Prescott 660 3.6Ghz and I have used that in a DS3 and I went for 5Ghz.
Never got it mind you but I really do think that was only down to temps, as I had been running it at 4.7 just fine 24/7
Now, for what its worth, when I disabled Hyperthreading on that CPU ( erm, that was 24/7 too ) and ran it stock ( Single Core @ 3.6 ) it was pretty much EXACTLY the same speed as my Daughters Socket 754 Newcastle 3000 when run at 2.4.
I ran numerous tests ( Nothgin scientific, just fun ) and in nearly all cases, it showed me that the Intel is on par wit hthe AMD when clocked 50% above the AMD.
So, a 1GHZ AMD = 1.5GHZ INTEL
2.4 AMD = 3.6 Intel
2.9 AMD = 3.6 Intel
And so on...
I have not done a head to head, but the C2D Intels v the P4 core seem to me, to be exactly quadruple.... I upped my Prescott 660 to an E6300 and obviously went from 3.6Ghz to 1.8 but while the MHZ halved, the actual speed, doubled.. plus the HT of the Prescott means that its fake dual core, while the E6300 is a proper dual core.