1. TechSpot is dedicated to computer enthusiasts and power users. Ask a question and give support. Join the community here.
    TechSpot is dedicated to computer enthusiasts and power users.
    Ask a question and give support.
    Join the community here, it only takes a minute.
    Dismiss Notice

Critical hyper-threading flaw discovered in Kaby Lake and Skylake chips

By midian182 ยท 14 replies
Jun 26, 2017
Post New Reply
  1. With Intel finally facing a challenge from AMD in the high-end processor market, the discovery of a major Hyper-Threading flaw in both Kaby Lake and Skylake CPUs would be a most unwelcome problem for Chipzilla. Unfortunately, that’s the scenario it’s now facing.

    The issue, which can destabilize chips and lead to unpredictable system behavior, data corruption, and data loss, was described on the Debian mailing list following earlier work by OCaml toolchain developers. It affects Skylake and Kaby Lake Intel Core processors (in desktop, high-end desktop, embedded and mobile platforms), Xeon v5 and v6 server processors, and some Pentium models. And while Debian is a Linux distro, the problem can appear on any operating system.

    This is how Intel’s errata documentation describes the flaw.

    Under complex micro-architectural conditions, short loops of less than 64 instructions that use AH, BH, CH or DH registers as well as their corresponding wider register (eg RAX, EAX or AX for AH) may cause unpredictable system behavior. This can only happen when both logical processors on the same physical processor are active.

    It's worth noting that the exact replication conditions, which aren't clear, are unlikely to be encountered by most users, but debian.org still recommends disabling hyper-threading until a microcode update is applied. Intel has reportedly issued some fixes, but they need to be integrated into motherboard BIOS/UEFI updates.

    The Debian notes says that “You want your system vendor to provide a BIOS/UEFI update that fixes Intel processor errata KBL095, KBW095 or the similar one for my Kaby Lake processor.” It recommends Skylake users contact their system vendor for an update that fixes "Intel erratum SKW144, SKL150, SKX150, SKZ7, or the similar one for my Skylake processor".

    Back in May, Intel responded to i7-7700K high-temperature issues by telling owners they shouldn’t overclock the chips. It’s a problem TechSpot's features editor Steve Walton touched on this in a video for Hardware Unboxed back in February.

    Permalink to story.

  2. GreenNova343

    GreenNova343 TS Guru Posts: 367   +251

    Wow...considering how long HyperThreading has been around, this is just really embarrassing for Intel. Hard to tout yourself as the industry leader when you break something that you first came up with...
    Darth Shiv and Uncle Al like this.
  3. VitalyT

    VitalyT Russ-Puss Posts: 4,533   +3,123

    Consider how long Intel has been the leader and that the flaw came up only now. And who's to say how many flaws AMD chips have that haven't been found just because their market share is near non-existent.
  4. trparky

    trparky TS Evangelist Posts: 556   +439

    Microsoft will probably issue a patch to the OS itself that loads new microcode at load time. It's not the first time Microsoft has done such a thing. It's happened before (example).
  5. evolucion8

    evolucion8 TS Enthusiast Posts: 32   +11

    You are clueless, don't forget that the Hyper Threading implemented on the Pentium 4 also had a flaw that would expose a vulnerability that allowed the hackers to analize hashes and retrieve passwords, or the 3770K, 4770K, 7700K issues with overheating. Don't even mention their horrible driver support with their IGPs. If Intel was the leader for so long, wasn't cause they were the best, it was cause they had no competition, thanks to Ryzen, Intel looks far less appealing that already it was.
  6. Scshadow

    Scshadow TS Evangelist Posts: 574   +228

    "analize hashes"?! Poor hashes...
  7. NahNood

    NahNood TS Addict Posts: 123   +64

    Non-existent? lol Every under-privileged poor(*) enthusiast including myself always buy AMD!

    (*)That is, those of us who like to build systems for half the cost and better spend the savings. hehe
  8. VitalyT

    VitalyT Russ-Puss Posts: 4,533   +3,123

    I said near non-existent. Don't quote someone by skipping the key words. And yes, AMD's market share of CPU-s is negligible today, as is the scrutiny for finding bugs in them.
  9. JaredTheDragon

    JaredTheDragon TS Guru Posts: 618   +394

    It seems like you're having trouble with diction here, as the word "negligible" doesn't mean what you think it means (contextually). As of May, AMD had (cough) risen above 20% again, and they've never fallen below 15% either. What's really negligible would be your opinion, evidently.

  10. Not impressed, my i7-6700K has already had a microcode patch (thru the UEFI I believe). So now is this #2?
    edit: after looking at the UEFI updates for my Asus mobo, the fix for this will be the third microcode update FWIW
    Last edited by a moderator: Jun 27, 2017
  11. Uncle Al

    Uncle Al TS Evangelist Posts: 5,511   +3,901

    If it's Intel they are considered "flaws"; now if it was Microsoft they would be "undocumented features" ....... oh yeah!
  12. evolucion8

    evolucion8 TS Enthusiast Posts: 32   +11

    LOL stupid autocorrector lol
    Darth Shiv likes this.
  13. Problem doesn't seem very serious in real life, only on paper. I'd suspect we would have heard about it from youtube tech bloggers and in other forums if it was a widespread problem. We now have 2 Skylake and 2 Kabylake processors in our use: i7-6700 (non-k) with 102.5000 BCLK and memory running at 2733 MHz (2666 HyperX fury), i3-6100 (stock speed and 2133 MHz RAM), i5-7200u and i7-7700HQ in 2 laptops. None of them have crashed or shown signs of errors, and believe me, except for the i3 all have been subject to torture tests in Prime95 and other benchmarks, as well as gaming, videoediting and handbrake compression sessions. And I'm sure Linus Tech or Jayz 2 cents or any other tech reporter would have mentioned it if any faults were found.. so my guess is this is more a "whitepaper" problem than a real-life issue. It "may" happen if one uses the cpu in a "specific" way and with "certain" calculations... So I'm not worried.
  14. Spect

    Spect TS Booster Posts: 33   +24

    AMD is looking better and better each day. Considering Ryzen, Epyc, the upcoming Vega, along with the crypto-currency boom (favouring AMD cards so much so that they can't make them fast enough and are out of stock everywhere.) and Intel dropping the ball when all eyes are on them to respond to the threat of losing their grip on the CPU market. Things are really looking up for them. Their CEO, Lisa Su who took over in 2014 (has been named one of the greatest leaders in 2017 by Fortune magazine) and I think we are starting to see some of the results and hopefully turn the company around... With $1000 bucks and the Robinhood app I made $200 just last week alone, just saying.
  15. Darth Shiv

    Darth Shiv TS Evangelist Posts: 1,967   +580

    What's even more embarrassing is they have persisted with Hyperthreading in the first place.

Add your comment to this article

You need to be a member to leave a comment. Join thousands of tech enthusiasts and participate.
TechSpot Account You may also...