Although chips including the Pentium 4 series could be overclocked or boosted beyond 4GHz before the arrival of AMD’s Bulldozer series, that was the first factory-clocked processor above 4GHz. The AMD FX-4170 offered an out of the box 4.2GHz frequency in early 2012. It packed 4 cores and 4 threads, used the AM3+ socket and was rated for a 125W TDP. The AMD FX-6200 shipped prior in December 2011 with a standard 3.8GHz clock that boosted to 4.0 – 4.1GHz frequencies.
AMD followed up with Piledriver in 2013 which included many 4GHz+ chips, most prominent being the FX-9590 with its 4.7GHz default frequency and 5.0GHz turbo.
Intel’s first consumer processor to be sold with a speed of 4GHz+ shipped in 2013 as the Haswell-based Core i7-4790K — perhaps most memorable as the ‘Devil’s Canyon’ launch — while the company’s 2017 Kaby Lake series also has a handful of parts shipped with a stock frequency at or above 4GHz.