AMD Ryzen 7000 CPUs actually improved their performance while leaving the Spectre V2 mitigations enabled by default. Previously, Intel and AMD’s CPU mitigations were designed to address bugs in software, which tended to reduce performance. Open source tech media Phoronix’s Michael Larabel did further testing of AMD’s Ryzen 7000 desktop CPUs, including the Ryzen 9 7950X and Ryzen 5 7600X.
Last week’s data results show that the AMD Ryzen 9 7950X in its “out of the box” state does nothing with Linux, faster than enabling the previous security mitigations.
AMD Ryzen 5 7600X CPUs can show positive results with security mitigations turned off in a small subset of tests, mostly in the numerous synthetic kernel benchmarks tested, but also in the just-released Linux 6.0 operating system.
However, OpenJDK Java, database workloads, some other workloads, and web browser tests negatively impacted Ryzen 5 7600X-based test systems when security mitigations were disabled.
In Spectre V1, from a Linux 6.0 perspective, Spectre V1 mitigates the _user pointer sanitization and usercopy/SWAPGS barriers, while disabling the speculative store bypass for SSBD/Spectre V4 security mitigations via prctl. Spectre V2 affects the system differently because of the inclusion of Retpolines, IBRS firmware, normal single-threaded indirect branch predictor, conditional indirect branch predictor barriers, and return stack buffer fill.
The latest AMD Zen 4 architecture is not affected by any known CPU security flaws.
Larabel also found that on his AMD Ryzen 5 7600X CPU test system, disabling the Spectre V2 mitigation had a huge negative impact on the performance of the Zen 4 architecture. However, when the Spectre V1 security mitigations are disabled, the performance impact is negligible.
Compared to Intel’s offerings and previous Zen cores, the AMD Zen 4 architecture is more optimized and responds better to Spectre V2 mitigations. Instead of disabling security measures for optimal performance, he advises users to keep the settings at their defaults.
