A few new sockets came out with Pentium 4. I know 423, 478, and
775 were used during this time.
It was based on the Netburst architecture, which was new with
this version of Pentium. Northwood was one of the new revisions of
pentium 4, that's new too.
The most gaping new technology was HTT. Hyperthreading
Technology, which actually did not premier with the Pentium 4, but
was developed late in the life of P4, and applied for the first
time here.