The Pentium 3 is what eventually topped out at 1.4 GHz, for the 130nm Tualatin parts introduced in 2001. The Pentium 4 started at 1.4GHz and 1.5GHz with the 180nm Willamette parts introduced in 2000. Those were eventually released with speeds up to 2.0GHz. The 130nm Pentium 4 Northwood reached 3.4GHz in 2004, and the 90nm Pentium 4 Prescott hit 3.8GHz later in 2004.