AMD's Chief Technology Officer, Mark Papermaster, looked to clarify the impact of Meltdown and Spectre on its expansive family of processors. With regards to Variant 1 (Spectre, Bounds Check Bypass), Papermaster says that AMD processors are in fact vulnerable. In this instance, the mitigation is possible via a patch for your current operating system.
The problem with the software patch, at least for AMD users running on Windows operating systems, is that the initial release ended up bricking computers. And further complicating matters, Microsoft in turn blamed poor AMD documentation regarding its chipsets for the problems.
"We are working closely with them to correct an issue that paused the distribution of patches for some older AMD processors (AMD Opteron, Athlon and AMD Turion X2 Ultra families) earlier this week," Papermaster clarified. "We expect this issue to be corrected shortly and Microsoft should resume updates for these older processors by next week."
As for Variant 2 (Spectre, Branch Target Injection), AMD believes that the uniqueness of its processor architecture "makes it difficult to exploit". However, it will make optional microcode updates available for Ryzen and EPYC processor beginning this week to address the exploit. These microcode updates will be used in conjunction with additional software patches to block the threat (Linux patches are being distributed now, while Windows patches are inbound).
Variant 3 (Rogue Data Cache Load, Meltdown) at this time is only [reportedly] attributable to Intel processors and does not affect processors from AMD.
What is unknown at this time is how overall system performance will be affected by these software patches and microcode updates for AMD processors. While Variant 1 and Variant 3 have little performance impact on Intel systems, Variant 2 can impact performance by 6 to 10 percent depending on the generation of processor being used (according to Intel's own tests) and the type of work being done on the system. Microsoft, for its part, says that Haswell or older systems will experience "more significant slowdowns".
AMD could find itself under more pressure if customers faces similar performance degradation on their systems.