https://arstechnica.com/gadgets/2018/01/heres-how-and-why-the-spectre-and-meltdown-patches-will-hurt-performance/

As the industry continues to grapple with the Meltdown and Spectre attacks, operating system and browser developers in particular are continuing to develop and test schemes to protect against the problems. Simultaneously, microcode updates to alter processor behavior are also starting to ship.