AMD's processors don't appear to have the exact same attack surface for the Spectre and Meltdown speculative execution vulnerabilities that Intel's chips have, but the systems with red beating hearts still need updates. Recently, a Microsoft Windows patch for the forementioned exploits caused boot failures on some AMD machines. After a temporary stoppage, Microsoft has now resumed pushing the update.
The update in question is KB4056892. It was suspended on all AMD systems on January 3 after reports of machines going into an unbootable state after application of the patch. The company determined that the problem was limited only to the oldest AMD Athlon X2-era systems capable of running Windows 10. The software company resumed updating newer AMD systems yesterday and says it will have a fix in place for older systems still not receiving the patch within a week.
According to Paul Lilly at PC Gamer, Microsoft blames errors in AMD's documentation rather than anything within its patch. The software giant reportedly said that "[it] has received reports of some AMD devices getting into an unbootable state after installation of recent Windows operating system security updates. After investigating, Microsoft determined that some AMD chipsets do not conform to the documentation previously provided to Microsoft to develop the Windows operating system mitigations to protect against the chipset vulnerabilities known as Spectre and Meltdown."
For its part, AMD responded to The Verge earlier this week, stating that it's aware of the issue and that both companies "have been working on an update to resolve the issue and expect it to begin rolling out again for those impacted shortly."
Whatever the cause, most AMD-powered systems are now receiving updates and those that aren't should be getting them soon.