Michael Larabel of the open-source tech outlet, Phoronix conducted further testing on AMD’s Ryzen 7000 Desktop CPUs, including the Ryzen 9 7950X and the Ryzen 5 7600X. The results from data revealed last week that the AMD Ryzen 9 7950X was faster when it was left untouched in its “out-of-the-box” state for Linux than to boot the kernel and deactivate the mitigations that were put in place. This time, utilizing an AMD Ryzen 5 7600X CPU with additional but minor software & hardware tweaks revealed that the same is true in the current Linux 6.0 operating system. Turning off the security mitigations in a small selection of tests revealed positive results, primarily with the numerous synthetic kernel benchmarks tested. However, OpenJDK Java, database workloads, several other workloads, and web browser tests negatively impacted the Ryzen 5 7600X-based testing system when disabling the security mitigations. In Spectre V1, from a Linux 6.0 perspective, Spectre V1 alleviates __user pointer sanitization and usercopy/SWAPGS barriers while the Speculative Store Bypass is disabled via prctl for the SSBD/Spectre V4 security mitigations. Spectre V2 affects the system differently because of the inclusion of Retpolines, IBRS firmware, always-on Single Threaded Indirect Branch Predictors, conditional Indirect Branch Predictor Barriers, and return stack buffer filling. The AMD Zen 4 architecture is not affected by any known CPU security vulnerabilities. Larabel also found that on his AMD Ryzen 5 7600X CPU test system, the disabled Spectre V2 mitigation dramatically affected the Zen 4 architectural performance negatively. However, the performance effect was negligible when disabling the Spectre V1 security mitigation. The author continued to discover that the AMD Zen 4 architecture is more optimized to react better against Spectre V2 mitigation than Intel’s offerings and previous Zen cores. He advises users to keep the settings in the default state instead of disabling the security measures for best performance.
