The Pentium 4 brand refers to Intel's line of single-core desktop and laptop central processing units (CPUs) introduced on November 20, 2000 and shipped through August 8, 2008. They had the 7th-generation x86 microarchitecture, called NetBurst, which was the company's first all-new design since introduction of P6 microarchitecture of the Pentium Pro CPUs in 1995. NetBurst differed from the preceding P6 (Pentium III, II, etc.) by featuring a very deep instruction pipeline to achieve very high clock speeds (up to 3.8 GHz) limited only by TDPs reaching up to 115 W in 3.4 GHz ?3.8 GHz Prescott and Prescotts 2M cores . In 2004, the initial 32-bit x86 instruction set of the Pentium 4 microprocessors was extended by the 64-bit x86-64 set.
Source[ Wikipedia ]