http://www.techradar.com/news/more-details-emerge-on-how-much-meltdown-and-spectre-patches-will-slow-down-your-pc

We’re finally hearing more concrete information about the real-world performance impact of the big Meltdown and Spectre patches, with Microsoft making some claims about a more serious slowdown for those using older Intel chips, and/or operating systems previous to Windows 10.

Remember that Intel’s initial line – following the original stories about the patches potentially slowing down PCs by up to an eye-watering 30% – was that the average PC user should not experience any ‘significant’ (i.e. noticeable) slowdown.