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Intel Skylake/Kaby Lake processors: broken hyper-threading ( Linux )

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#1 NickAu


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Posted 27 June 2017 - 01:48 AM

Click the link for a full explanation and fix.

This advisory is about a processor/microcode defect recently identified
on Intel Skylake and Intel Kaby Lake processors with hyper-threading
enabled. This defect can, when triggered, cause unpredictable system
behavior: it could cause spurious errors, such as application and system
misbehavior, data corruption, and data loss.

It was brought to the attention of the Debian project that this defect
is known to directly affect some Debian stable users (refer to the end
of this advisory for details), thus this advisory.

Please note that the defect can potentially affect any operating system
(it is not restricted to Debian, and it is not restricted to Linux-based
systems). It can be either avoided (by disabling hyper-threading), or
fixed (by updating the processor microcode).

Due to the difficult detection of potentially affected software, and the
unpredictable nature of the defect, all users of the affected Intel
processors are strongly urged to take action as recommended by this


Edited by NickAu, 27 June 2017 - 02:02 AM.

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#2 Condobloke


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Posted 27 June 2017 - 03:01 AM

I would have to wonder if disabling intel microcode firmware might achieve a good outcome...?



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#3 jonuk76


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Posted 27 June 2017 - 06:23 PM

AFAIK CPU microcode updates are normally issued via motherboard firmware updates, as and when Intel release them.


I've also got the above showing in Driver Manager on Linux Mint on the system I'm using right now.  I really don't know what it is, and am not really in the mood to mess with it to find out!!  It's an older (Haswell) system, rather than Skylake/Kabylake therefore, unaffected by this bug.


#4 cat1092


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Posted 29 June 2017 - 05:56 AM

AFAIK CPU microcode updates are normally issued via motherboard firmware updates, as and when Intel release them.


I've also got the above showing in Driver Manager on Linux Mint on the system I'm using right now.  I really don't know what it is, and am not really in the mood to mess with it to find out!!  It's an older (Haswell) system, rather than Skylake/Kabylake therefore, unaffected by this bug.


+1! :thumbup2:


Same here, am glad that I purchased both Devil's Canyon CPU's released, in both the more popular i7-4790K & it's little brother, the i5-4690K, which if overclocked to a x44 ratio (all cores), will run at the stock frequency of the 4790K, and performs well w/out the 'benefit' of H/T. For that matter, the i5 is a far better seller than the more costly i7 of any gen 'i' series, the reviews states for themselves how good the i5 desktop CPU is. Notebook i5's are dual core, so has the benefit of H/T. 


By chance also have a i7-4770 that shipped with my XPS 8700, and nothing I do bogs it down, as well as the other two Haswell CPU's mentioned above. I'm happy not to have been swept into the trap of the 6th gen quads onward, the i7-7700K is well known to have sudden heat spikes at just the movement of of the mouse, some buyers has actually reported getting an 'engineering sample' in a retail boxed i7-7700K. One of which being a prominent UK based site that not only has a Worldwide tech Forum, also performs extensive testing of hardware pre & post release, in this case, Tom's Hardware, trusted by many enthusiasts. Their testers wanted to investigate the heat spike issue all on independent computers w/out sharing of data between them to create a level playing field, so went to a local retailer & purchased either 25 or 50 retail boxed i7-7700K CPU's. To their surprise, one was clearly a sample, had "Intel Confidential' stamped on it, wow talk about Intel QC, they can't even designate torture tested CPU's from brand new ones, let alone build these right (still using thermal paste as a substitute for fluxless solder). Who knows how long that sample had been in their lab & what grueling tests performed? Plus the S/N didn't match what was on the box, so that meant voided warranty from the start. Proof of such would had been the burden of the customer, unless (unusually) opened & inspected at the retailer with a witness (sales associate) present. Most carries these home, some opens as soon as walking through the door, others like myself may take up to 3-4 weeks to open, just inside of the RMA window.


Fortunately, after all of Tom's tests were performed, the sample was in line with the others & the heat issue was determined to be true & not just 'normal activity', as Intel has implied, looking to avoid what'll certainly be a large class action lawsuit (give it a few months & don't RMA the CPU except for refund only). 


Am glad that my Haswell CPU's doesn't suffer from this issue, plus all runs cool on air alone, I don't do liquid cooling. Will be upgrading the CPU cooler on the XPS 8700 very soon to a well known low profile cooler that'll be more efficient than the stock aluminum block that Dell provided with fan. While it's heavy, aluminum cannot beat the cooling of a also heavy multi copper tube cooler, will post any 'before & after' results once performed. Just happy to discover one that'll work, using optical drive screws for the mounting brackets. :)


While the Intel microcode update is optional, I install it, by chance it's also installed via Windows Update, unless one knows the exact update to look for. Have had no negative issues to report since 2013 when the XPS 8700 was purchased, and last year, the i7-4790K, plus this year, the i5-4690K, all has the Intel microcode update. To the best of my knowledge, the only ones who were negatively affected were those who purchased unlocked Pentiums, the update (am not certain if it was on Windows or Linux) enabled the lock on the CPU & cannot be overclocked afterwards. Intel assumes no responsibility for this, it's up to the use to know what's going on. That's why I applied the microcode update, from what I discovered, my CPU's weren't negatively affected. So far, only certain unlocked Pentiums, and really, what true enthusiast would touch a sub-$100 CPU for their overclocking activities. as well as gaming/benchmarking? The only use I'd have for such a CPU would be to practice delidding, in case the temps of my main CPU's begin to rise & can't control with cleaning heatsink & fan (or tower cooler), repasting & reassemble. :)


The Haswell line will likely be my last Intel upgrade, even with Ryzen, is still doing things the right way, just like the 'FX' lineup, no onboard GPU, which should be shifted back to where it was, the MB OEM's. So should AMD continue to show progress, will go with their CPU's come time for complete system upgrades, one at a time, as necessary At least AMD soldiers their IHS to the die for best cooling & durability, the main reason why there's many Intel Core 2 Duo's & Quads (as well as P4's) still kicking, plus older AMD CPU's. The best thermal pastes would had long ago dried out in these. :thumbsup:



Performing full disc images weekly and keeping important data off of the 'C' drive as generated can be the best defence against Malware/Ransomware attacks, as well as a wide range of other issues. 

#5 pcpunk


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Posted 29 June 2017 - 10:55 AM


cat1092: While the Intel microcode update is optional, I install it,

Do you check it against what is already installed?  On one of my pc's the one offered was older than the one installed.


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#6 GoofProg


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Posted 29 June 2017 - 02:13 PM

Yes, Intel microcode... how wonderful.  You know... maybe recompiling the kernel may help somehow.  In this way, you can set the kernel to use a specialized processor code.  I dunno recently but I know it used to have the option to compile Intel Dual Core 2 code from the last time I looked.

#7 Ubiq


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Posted 03 July 2017 - 07:58 PM

I'm about to buy a pc with one of these processors. Should I wait, or is this no big deal?

Machine: Toshiba Portege r705-P41, Dual Boot: MS Windows 7 Home Premium 64-bit; Ubuntu 15.04
CPU: Intel Core i5 460M @ 2.53GHz Arrandale 32nm Technology,
RAM: 4.0GB Dual-Channel DDR3 @ 532MHz (7-7-7-20), Motherboard: TOSHIBA Portable PC (rBGA1288 Socket)
Video Card: Intel HD Graphics Revision 2 1720 MBytes


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