https://www.theregister.co.uk/2018/01/08/microsofts_spectre_fixer_bricks_some_amd_powered_pcs/

Microsoft’s fix for the Meltdown and Spectre bugs may be crocking AMD-powered PCs.

A lengthy thread on answers.microsoft.com records numerous instances in which Security Update for Windows KB4056892, Redmond’s Meltdown/Spectre patch, leaves some AMD-powered PCs with the Windows startup logo and not much more.