Phoronix published Benchmarking AMD FX vs. Intel Sandy/Ivy Bridge CPUs Following Spectre, Meltdown, L1TF, Zombieload A quote from the article:

Now with MDS / Zombieload being public and seeing a 8~10% performance hit in the affected workloads as a result of the new mitigations to these Microarchitectural Data Sampling vulnerabilities, what's the overall performance look like now if going back to the days of AMD FX Vishera and Intel Sandybridge/Ivybridge processors? If Spectre, Meltdown, L1TF/Foreshadow, and now Zombieload had come to light years ago would it have shaken that pivotal point in the industry? Here are benchmarks looking at the the performance today with and without the mitigations to the known CPU vulnerabilities to date.

 Benchmarking AMD FX vs. Intel Sandy/Ivy Bridge CPUs Following Spectre, Meltdown, L1TF, Zombieload