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Intel Core i5 8400 vs. i5 9400F Meltdown/Spectre/L1TF/MDS Mitigation Impact

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  • Intel Core i5 8400 vs. i5 9400F Meltdown/Spectre/L1TF/MDS Mitigation Impact

    Phoronix: Intel Core i5 8400 vs. i5 9400F Meltdown/Spectre/L1TF/MDS Mitigation Impact

    With recently seeing a deal on the Intel Core i5 9400F processor, I picked it up for testing as part of our Spectre / Meltdown / Foreshadow / Zombieload testing since it features some hardware mitigations and is otherwise quite similar to the unmitigated Core i5 8400 that I also have in the benchmarking farm. Here are some results when benchmarking the Core i5 8400 and Core i5 9400F with and without the current Linux mitigations for these CPU vulnerabilities.

    http://www.phoronix.com/vr.php?view=27948

  • #2
    I was wondering... are those hardware mitigations not correctly detected (and thus, more mitigations were active than actually needed), or were only the needed ones active and the hardware ones have no large impact?

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    • #3
      Then the next question is which generation without mitigations would be equal to the new processors with mitigations

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      • #4
        Originally posted by tchiwam View Post
        Then the next question is which generation without mitigations would be equal to the new processors with mitigations
        I think you meant the other way around, with mitigations performing equally to without mitigations

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        • #5
          Originally posted by oleid View Post
          I was wondering... are those hardware mitigations not correctly detected (and thus, more mitigations were active than actually needed), or were only the needed ones active and the hardware ones have no large impact?
          According to Intel some hardware mitigations still require software support. It would be amusing if Intel managed to get the detection logic wrong for their own CPUs

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          • #6
            What about the new LeadPipe attack? The one where a hacker breaks into your room while you are logged into your computer and knocks you over the head with a lead pipe, and then has full access to your system?

            I've heard the only known workable mitigation is to unplug the computer and/or disable any batteries. I'd like to see benchmarks if possible.

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            • #7
              it's looking like the "hardware" "in-silicon" mitigations are just the newer performance reducing microcode burned into the chip's ROM. At-least with the 8400 one has the choice of using the older microcode to get the performance back.

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              • #8
                Originally posted by andyprough View Post
                What about the new LeadPipe attack? The one where a hacker breaks into your room while you are logged into your computer and knocks you over the head with a lead pipe, and then has full access to your system?

                I've heard the only known workable mitigation is to unplug the computer and/or disable any batteries. I'd like to see benchmarks if possible.
                well, if we are benchmarking the LeadPipe, we would also have to test the Lumber2x4 vector too

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                • #9
                  Originally posted by esmth View Post
                  it's looking like the "hardware" "in-silicon" mitigations are just the newer performance reducing microcode burned into the chip's ROM. At-least with the 8400 one has the choice of using the older microcode to get the performance back.
                  That is the most likely scenario IMHO. With the newer microcode shipping out of the box, Intel still can disable mitigations on OS-level to make CPUs look better in certain benchmarks

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                  • #10
                    For 9th gen Coffee Lake desktop users, the existing CPUs (9900K, 9700K, 9600K, 9400F) feature HW mitigation for 1 out of the 4 vulnerabilities.
                    A subsequent revision was announced to be 4/4. These CPUs were announced on April 23rd and will likely hard launch in the June/July time-frame. Existing CPUs will receive software-based mitigation, which can degrade performance in some areas. Gaming performance degradation is generally <1%.
                    You do not need to disable Hyper-Threading. Because of the way that this attack works, and the way that it obtains data, you are at an extremely low risk for it. It's the data-centers and cloud-storage providers that need to take additional steps on a case-by-case basis.


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