The first CPU to reach a clock speed of 4 GHz was the Pentium 4 570 released in November 2004 as part of Intel's NetBurst microarchitecture, but this milestone wasn't achieved out of the box.

Intel's top Pentium chip, introduced in late 2000. The successor to the Pentium III, the Pentium 4 features the NetBurst micro-architecture (see NetBurst). All Pentium 4 chips are single core ...

Intel 486, Celeron, Itanium, Pentium, and XScale. There are four product lines of AMD CPU chips: Athlon, Duron, Opteron, AMD-K6 and Geode. CPU chips in the Athlon family feature an x86 architecture ...

The most recent Atom used in laptops is from 2016 and it was hardly fast back then. Up until recently, there were separate brands for Celeron and Pentium processors. Intel has now bundled both of them ...

Case in point an original (P54C) Intel Pentium ... which offer a range of speed, gain and output impedance advantages that are beneficial for some part of a CPU compared to CMOS.