Microsoft’s Spectre V2 Patch Kills Performance on Some AMD APUs

The Spectre mitigations are supposed to cause a small CPU performance hit (somewhere along the lines of 5-10%). And for most processors, that is what I have observed. But for certain AMD APUs, the hit has been much larger—in the 500-1,000% range.

So far, I have only observed these symptoms on AMD A6-9220 and A10-9600P APUs. I don’t see these symptoms in other AMD APUs, like the A8-3250M, A9-9420, or the Ryzen 5 2500U (they don’t call it an APU anymore, but it is still an integrated CPU and GPU).

The symptoms are as follows: every activity is heavily CPU intensive. Just moving the mouse rapidly using the trackpad can pump the Synaptic driver CPU usage to 35%. Loading a standard website with any browser can take 60-120 seconds with the CPU pegged at 100% the entire time.

Disabling the Spectre V2 mitigations using the two registry keys described in the website below restores performance to expected levels.

https://support.microsoft.com/en-us/help/4073119/protect-against-speculative-execution-side-channel-vulnerabilities-in

Hopefully this is something that Microsoft fixes in the near future.  They have already revised their Spectre patches several times.  But I’m not holding my breath.