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[MAIN\MERGED] Intel Skylake & Kaby Lake Hyperthreading Bug

Level 7
It has been confirmed that Intel's Skylake/Kaby Lake hyper-threading can present serious issues that can be fixed by a BIOS/UEFI update that targets Intel processor errata KBL095, KBW095 or the similar one for Kaby Lake processor.

Any plans for such update to come? On Kaby Lake it seems the most safe route at the moment is to simply disable hyper-threading until ASUS provides a new BIOS that addresses this. On Skylake there's the option on ArchLinux side, for example, to install extra/intel-ucode to get microcode updates since there's a fix in revision 0xb9/0xba and later. Windows doesn't have a microcode update for this yet, afaik.

133 REPLIES 133

Level 7
Have you already heard from this news:

Does anybody know if there is a fix available from Asus yet?

Would very much like to know as well, latest BIOS release notes say nothing about it:

MAXIMUS VIII GENE BIOS 3401 - 2017/04/07 update
1.Improved System Performance
2.Modified OA key function in legacy OS
3.Fixed some PS/2 devices connection issue in win8/win10 when fast startup is enabled
4.Fixed chassis fan’s behavior after wake up from S3
5.Fixed CPU(i3-7350K) ratio item missing issue in SW

any updates about the Z270F Gaming bios update/fix for the hyper threading and turbo boost !!?

i have built a new rig with the Z270F Gaming and the i7-7700k !!
for 2 days i struggled to install the os Win7/win10 and the only way to make the OS install and work correctly is to disable turbo boost and hyper threading in bios !!
i already have updated the bios (v1301 i think) but no chance to the OS to work when turbo boost or hyper threading are enabled.
so now i feel like i am using an i5 7th gen. instead of an i7 !
Please advise

Broken Hyperthreading. "(Dangerous) application and system misbehaviour, data corruption, and data loss" (with any OS) under certain specific conditions.

"Disable Hyperthreading immediately in unfixed systems. Contact system vendor to obtain an updated UEFI/BIOS which implements the fix."

Intel microcode packages which fix this are available for some affected platforms and operating systems.

I'm actually surprised such a serious bug remained unnoticed (and unfixed) for so long. Apparently the "specific conditions" which cause this bug must occur very infrequently and/or generally compromises system data in "noncritical" ways.

On the plus side:
- this doesn't affect Core i5 parts (because they lack HT)
- this doesn't seem to present apocalyptic risk when gaming (because most games make poor or downright awful use of multi-threading - 4C/8T typically being roughly equivalent to 5C/5T, at best - and very few games running outside of VMs could/would use even 4 physical cores anyhow, let alone 8 virtualized cores)

But if you're not able to easily restore your WinOS and all your data (from a backup image or from scratch) then disable HT in BIOS and keep it disabled until this erratum gets fixed, lol, chance of failure appears very low but consequence of failure could be catastrophic!

Also being discussed in this thread.
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Korth wrote:
this doesn't seem to present apocalyptic risk when gaming

You sure about that? I'm wondering if this is the lockup/freeze during gaming bug that has plagued me (and others across different mb brands) since Skylake launched.

I haven't experienced any crashes whatsoever, and on top of gaming I even develop heavily multi-threaded software with this workstation, but just to be on the safe side I:

1) Got extremely pissed off
2) Disabled HT

I hope to see a new BIOS with the uCode update really soon.

no need to panic, just update your CPU Microcode to latest version. and good thing there is an application that does it for you automatically.


I use this tool to update my CPU Microcode Automatically to latest which is Version BA !


Haha, thanks for mentioning it, but I'm too paranoid to use a third party tool that offers no source code I can compile myself and binaries that are hosted on a ".ru" domain or on mega.

This is on Asus, I'll be on 4 threads until the new bios comes out, and if it takes too long I'll start *****ing around 😄

Double thanks for telling me which version is the latest one! At least I'll know for sure when I have it.