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Intel has published its own set of benchmark results for the mitigations to the latest round of vulnerabilities, but Phoronix, a publication that focuses on Linux-related news and reviews, has conducted its own testing and found a significant impact. Phoronix's recent testing of all mitigations in Linux found the fixes reduce Intel's performance by 16% (on average) with Hyper-Threading enabled, while AMD only suffers a 3% average loss. Phoronix derived these percentages from the geometric mean of Linux test results from its test suite.
From a performance perspective, the overhead of the mitigations narrow the gap between Intel's Core i7-8700K and i9-7980XE and AMD's Ryzen 7 2700X and Threadripper 2990WX processors. It's notable that neither of the Intel chips feature the in-silicon mitigations that come with the company's newer chips.
Intel's chips can suffer even more with Hyper-Threading (HT) disabled, a measure that some companies (such as Apple and Google) say is the only way to make Intel processors completely safe from the latest vulnerabilities. In some of Phoronix's testing, disabling HT reduced performance almost 50%. The difference was not that great in many cases, but the gap did widen in almost every test by at least a few points.
To be clear, this is not just testing with mitigations for MDS (also known as Fallout, Zombieload, and RIDL), but also patches for previous exploits like Spectre and Meltdown. Because of this, AMD also has lost some performance with mitigations enabled (because AMD is vulnerable to some Spectre variants), but only 3%.
AMD's processors are immune to the latest round of vulnerabilities, and its users also don't need to turn off Simultaneous Multi-Threading (or SMT), which is like Intel's HyperThreading, because AMD processors do not have any known security faults when SMT is enabled. Users with Zen-based processors will likely never notice the difference.
"If looking at the geometric mean for the tests run today, the Intel systems all saw about 16% lower performance out-of-the-box now with these default mitigations and obviously even lower if disabling Hyper Threading for maximum security. The two AMD systems tested saw a 3% performance hit with the default mitigations. While there are minor differences between the systems to consider, the mitigation impact is enough to draw the Core i7 8700K much closer to the Ryzen 7 2700X and the Core i9 7980XE to the Threadripper 2990WX." - Phoronix
The performance reduction that correlates with these security patches is a challenge for Intel, coming in at a time when Intel's chips are vulnerable to AMD's upcoming desktop and server CPUs that will arrive with a smaller 7nm manufacturing process. In many cases, the mitigations reduce Intel's performance advantage over the existing Ryzen processors, and there is little doubt the next-gen Ryzen chips will be even faster. That could have an impact on both the desktop PC and server markets.
Phoronix says, "While there are minor differences between the systems to consider, the mitigation impact is enough to draw the Core i7-8700K much closer to the Ryzen 7 2700X," which bodes well for AMD's 7nm Ryzen 3000 CPUs. Although Intel may retain the gaming crown, AMD's potential improvements in clock speed, IPC, and core count (with Ryzen 3000 theoretically capping out at a staggering 16 cores) will certainly make for an interesting competition in the coming months.