https://www.bleepingcomputer.com/news/microsoft/windows-10-kb4100347-intel-cpu-update-causing-boot-issues-and-pushed-to-amd-users/

On August 21st, Microsoft released an update to the May KB4100347 security update for Windows 10 and Windows Server 2016, which contain Intel CPU microcode updates to mitigate Spectre vulnerabilities. After installing this latest version, Windows users are reporting that they are unable to properly boot Windows 10 or are having performance issues. To further complicate the issue, this Intel CPU update is also being pushed to users of AMD processors.

It is not known what has been changed in the August 21st KB4100347 revision as Microsoft has not updated the support article since July 24th 2018. What we do know, is that since being offered via Windows update there have been numerous reports of Windows 10 machines no longer being able to boot, being stuck in a infinite automatic repair loops, or performance issues when playing music, using Chrome, or other applications.