[WARNING] Intel Skylake/Kaby Lake processors: broken hyper-t

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[WARNING] Intel Skylake/Kaby Lake processors: broken hyper-t

Postby pylkko » 2017-06-25 17:40

[WARNING] Intel Skylake/Kaby Lake processors: broken hyper-threading
https://lists.debian.org/debian-devel/2 ... 00308.html
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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby Wheelerof4te » 2017-06-26 21:11

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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby /tmp » 2017-06-28 14:54

It's times like this that I'm glad I have my troll-worthy Pentium G3258 :D
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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby ticojohn » 2017-06-29 20:49

I am using Intel i5 processors in both of my computers. i5 processors are supposed to NOT support hyper-threading. When I look at, for instance, cat /proc/cpuinfo I see that there are 4 cores and 4 siblings, ergo no hyper-threading. However, when I look at the flags, in /proc/cpuinfo, I see that the ht flag is set. Isn't that strange? Maybe a bios setting although I don't find anything called Hyper Threading. And NO, I am not looking for a support answer. It's more of a rhetorical question.
I'm not irrational, I'm just quantum probabilistic.
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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby acewiza » 2017-06-29 21:18

The story about it I read suggested this was not a very big deal - invoked only in specific, rare use cases.
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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby stevepusser » 2017-06-29 21:42

It depends on the type of i5 processor as to whether it supports hyperthreading or not. Mine happens to.

Code: Select all
inxi -x -C
CPU:       Dual core Intel Core i5-6200U (-HT-MCP-) cache: 3072 KB
           flags: (lm nx sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx) bmips: 9600
           clock speeds: max: 2301 MHz 1: 400 MHz 2: 2300 MHz 3: 2300 MHz 4: 400 MHz


I already installed the intel-microcode update that's supposed to fix it in Linux, as well as the "BIOS" update from Acer from the 26th that I suspect fixes it for the machine overall. I noticed that the BIOS updater seems to have changed from a Windows-only program to a DOS one that Linux users can use FreeDos to install, so Acer deserves some kudos for that.
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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby ticojohn » 2017-06-30 12:26

stevepusser wrote:It depends on the type of i5 processor as to whether it supports hyperthreading or not. Mine happens to.

Right on Steve. I am using 4th and 5th generation i5 processors which do not support hyperthreading. I believe that hyperthreading for the i5 was introduced in 6th generation, however there might have been some 5th gen processors that supported it. Still wish I knew why the "ht" flag is set even though the CPU I have doesn't support it. I've gone through the BIOS and find no reference to hyperthreading. Might be called something else, maybe Virtualization?

Whatever, they work and I'm not messing with what ain't broken.
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Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyp

Postby ticojohn » 2017-06-30 22:37

stevepusser wrote:It depends on the type of i5 processor as to whether it supports hyperthreading or not. Mine happens to.

After doing some checking I find that i5 processors with 4 cores do not hyperthread. The i5 processors with 2 cores, such as yours, do have hyperthreading. If the 4 core i5 had hyperthreading it would essentially be an i7.
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