Core solo/duo was the last in the P3 heritage (but that heritage itself traced all the way back to the Pentium Pro initially) via the 2 generations of Pentium-M (even if Core2 had parts they were 64bit so more of a major upgrade).

Whoever convinced the execs at Intel to put Pentium-M into production as a "mobile" chip really saved them when NetBurst reached it's end of line, I owned a first-generation Pentium-M laptop and it was really superb (seeing the Macbook Air introduced was a big meh).

It was really a turning point though, I remember posting some compile time and people didn't believe me, but the Pentium-M chips were good at compiling (since compilers are kinda "branchy" when it comes to execution in a way P4 didn't "like") but also because I had maxed out the RAM on the machine (1.25gb when 256mb was the base for the machine and similar for many desktops) so much of the code and libraries could be retained in disk caches.

With portable performance like that, why do you need a desktop?