Earlier this week, a new variant of the Specter vulnerability surfaced. Early reports suggested that only Intel and Arm processors were affected, but a short while back, it was discovered that AMD’s entire Ryzen family was vulnerable as well. The earlier released “LFENCE/JMP” method used to mitigate the flaw in Ryzen processors has been deemed ineffective. In case you have forgotten, Specter and Meltdown allow attackers to steal sensitive data from microprocessors by exploiting speculative execution.
On Intel’s side, VUSec has advised the implementation of eIBRS (Enhanced Indirect Branch Restricted Speculation) in addition to existing retpoline mitigations to fight off BHI. AMD, for the time being, is advising the use of “generic”.
The primary impact of these mitigations can be seen in workloads relying on I/O functions while mainstream applications such as image manipulation, browsing, and gaming are more or less unaffected. Going by Phoronix’s tests, the Core i9-12900K saw a drop of up to 26.7% in performance, with most I/O related tasks seeing a 5-14% loss.
Mobile SKUs, in this case, the Core i7-1185G7, see a much larger hit. Interestingly, the kinds of workloads affected are also different. OSBench plummets by as much as 35.6% while IO Tester drops by a similar 34%. Luckily, workloads not depending on I/O or system admin aren’t impacted much.
Although AMD’s Ryzen processors are also affected, the performance deltas are much smaller. Most of the drops are under 5%, with even the largest ones (OSBench, SockPerf) not crossing the 10% mark. Stress-NG is the only notable deficit with a massive loss of 54% on the Ryzen 9 5950X.