What's odd or fishy? Overly hardcore hardware mitigations making software mitigations moot seems logical enough.
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With AMD Zen 4, It's Surprisingly Not Worthwhile Disabling CPU Security Mitigations
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Originally posted by kozman View PostThat's the most counter-intuitive thing I've ever seen. All other benchmarks of the past showed that mitigations=off much improved perf at the expense of security. So does this imply AMD designed Zen 4 with the assumption of mitigation=on as a means of protecting users from themselves and disabling will cost you perf if you do? Carrot + stick?
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AMD has probably tweaked the hardware itself and the microcode to react better to the kernel behaviour when mitigations are enabled, which makes all the sense in the world given that most people will run the kernel at default settings.
If you know that some kernel paths are going to behave in an unoptimal or strange way, you can prepare the silicon to react as good as it can to it. Of course, if you disable all mitigations, the kernel will not behave as it is supposed to do at stock settings and the CPU will underperform, even if it's supposed to work faster that way. Think of it as a branch misprediction.
It's not fishy at all. I expect Intel to do the same on Rocket Lake.Last edited by EvilHowl; 30 September 2022, 05:23 PM.
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No you are not going to see any performance boost turning off mitigation's, lets just put it this way... Zen 4 and Raptor Lake are so fast that GPU's are actually bottle necking the CPU's. I thought my 5800x was ludicrous speed. We are now in a CPU performance territory where the newest CPU's coming out are absolutely space balls, mega maid is going from suck to blow, that's how fast they are.
Kindest courtesy,
Dark HelmetLast edited by creative; 30 September 2022, 03:13 PM.
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Originally posted by EvilHowl View PostAMD has probably tweaked the hardware itself and the microcode to react better to the kernel behaviour when mitigations are enabled, which makes all the sense in the world given that most people will run the kernel at default settings.
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Originally posted by mahurinj View PostWasn't one of the benefits of Zen 4 that some/most of these vulnerabilities were addressed at the hardware level?
If these vulnerabilities are addressed at the hardware level, that would explain a lot.
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