Intel Disables TSX for More CPUs via Microcode Updates

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Intel users will soon trade performance for security once again. Phoronix reported that recent microcode updates would disable Intel Transactional Synchronization Extension (TSX) by default on the company's 6th, 7th, and 8th Gen processors. Disabling the feature is supposed to make those CPUs more secure, but it's also expected to result in worse performance in tasks that benefited from using TSX.

Phoronix said these updates were prompted by a memory ordering issue in TSX. A whitepaper (PDF) suggests Intel has been aware of the issue since June 2018, and the company released microcode updates to address the flaw in October 2018. Still, it's taken almost three years to release updates that disable TSX by default. Those updates were included with Intel Platform Update 2021.1 when it debuted on June 8.

"Workloads that were benefited from Intel TSX might experience a change in performance," Intel said on June 12. It also said that "some advanced users of performance monitoring (Perfmon) may need to change their collection scripts and methodologies" due to the microcode updates. The company didn't offer more information about the performance hit to tasks affected by these changes.

But there's good news: Intel said that it "does not expect these microcode updates to affect users who do not use the [Performance Monitoring Unit], or who only use updated PMU drivers and tools," though it does "recommend that PMU driver developers and performance tool developers follow the guidance in this document." The average person is unlikely to notice significant changes in performance.

Developers have already prepared the Linux kernel for these microcode updates. Phoronix noted that patches meant for Linux 5.14 made this change: "Add support for new Intel microcode deprecating TSX on some models and do not enable kernel workarounds for those CPUs when TSX transactions always abort, as a result of that microcode update." That support might also make its way to Linux 5.13.

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Nathaniel Mott
Nathaniel Mott
Freelance News & Features Writer

Nathaniel Mott is a freelance news and features writer for Tom's Hardware US, covering breaking news, security, and the silliest aspects of the tech industry.

6 Comments Comment from the forums
  • linuxdude
    This is really embarassing - Intel simply disables functionality, customers explicitly paid for (TSX is only available in the higher "grade" chips / enterprise chips - and deliberatly fused off in the cheaper entry-level products). So you paid tons of money for an i7 and whoops, one of the features used for product differentiation is simply turned off.
    Reply
  • ry138
    Very interesting, I realize the 8th gen CPU's are included, but I wonder if this microcode update will allow for 6th and 7th gen support in Windows 11?
    Reply
  • Soaptrail
    I am confused, why is this needed as the article states, "the company released microcode updates to address the flaw in October 2018. " so if the microcode from Oct18 fixed it why turn it off 3 years later?
    Reply
  • mdd1963
    My GOD! I simply cannot and will not tolerate the loss of TSX!!!!!!!!
    (Which I had never heard of prior to this article, and, cannot yet list a single app which would be affected!) :)
    Reply
  • Johnpombrio
    mdd1963 said:
    My GOD! I simply cannot and will not tolerate the loss of TSX!!!!!!!!
    (Which I had never heard of prior to this article, and, cannot yet list a single app that would be affected!) :)
    LOL. I felt the same when the Spectre/Meltdown fixes were put into place. Headlines painted a dire picture of large decreases in performance and THUD nothing seemed to change a bit. Even the most affected server pronouncements of doom failed to occur once programmers worked on the performance dips. (Here is where I expect some posters to fling some charts from the old performance hits from S/M back in 2019 without any mitigations that have been implemented since). There may be some changes here or there, but compared to going from, say, a hard drive to SSD, these are unnoticeable blips.
    Reply
  • Soaptrail
    Johnpombrio said:
    LOL. I felt the same when the Spectre/Meltdown fixes were put into place. Headlines painted a dire picture of large decreases in performance and THUD nothing seemed to change a bit. Even the most affected server pronouncements of doom failed to occur once programmers worked on the performance dips. (Here is where I expect some posters to fling some charts from the old performance hits from S/M back in 2019 without any mitigations that have been implemented since). There may be some changes here or there, but compared to going from, say, a hard drive to SSD, these are unnoticeable blips.

    Agreed but those minor blips are amplified in benchmarking CPU's when everyone is determining who is better, AMD or Intel.
    Reply