"Finally, I thought an interesting note that was made was about there being two design teams at AMD: a server and a mobile product team. This may seem against initial reasoning as so much of AMD's processor sales are based on desktop parts. However, Richard claimed that currently what we have is a situation where a server processor (Opteron) was changed and tweaked slightly to be called a desktop processor (Athlon 64). In the not to distant future we might see the reverse in that a mobile processor would be tweaked and changed enough to be called a desktop processor. Perhaps some indiciation of our changing market place? Food for thought, indeed."
As you know, the Xeon Foster is called "Willamette with SMP support", and the Xeon Prestonia is known as "Northwood with SMP support". These CPUs are based on the same core. Besides, the pairs of "Foster - Willamette" and "Prestonia - Northwood" are based on the same fabrication process and have the same L2 cache size. The processors have different sockets, but if you look at the signal assignment diagram the pins of the Socket 603 processor will show that most of them control either power supply or ground, i.e. they are not significant.