Northwood
The new Pentium 4s by Intel with new Northwood core at 2.0 and 2.2 GHz got released in January 2002.
Northwood had an increase in the secondary cache size from 256k to 512k (transistor count increased from 42 million to 55 million) had a transition to a new 0.13 micrometer (130 nm) fabrication process with a new socket, socket 478.
Chips were capable of running at the same speed producing less heat, or even run at higher clocks when the chip was made out of smaller transistors.
In April 2002 a 2.4 GHz P4 was released which was followed by a 2.53 GHz part in May (the bus speed was increased from 400MHz to 533MHz), 2.6 and 2.8 GHz parts in August, and a 3.06 GHz Pentium 4 in November. The P4s in the 2.4 to 2.8 GHz range were definitely the fastest chips available in the market.
Mainly the difference in all these new versions was that they all supported Hyper -Threading , and ran their system buses at 800 MHz.
