https://wccftech.com/windows-10-2019-spectre-v2-slowdowns/

Microsoft is currently pushing out new Preview Builds from Windows 10 2019 edition to Insiders in Skip Ahead and Fast Ring. Along with other improvements and features, it looks like the next version of the desktop operating system carries a mitigation for the Spectre v2 speculative execution side-channel attack that will stop the machines from slowing down.

When the companies hustled to address Spectre and Meltdown vulnerabilities, one of the major concerns was the reduced performance of the PCs. Mitigation, in some tests, showed a severe impact on performance that could go from 5% to 30%. Intel’s microcode mitigations for Spectre variant 2, tracked as CVE- 2017-5715, were specifically of concern as they change how hardware speculatively executes.