Intel Hyperthreading Bug Unearthed In Kaby Lake And Skylake Processors

[darth_adversor]

This news literally comes a week after my wife surprised me with a new laptop, running an i7-7700HQ. Just my luck.

 

[__Isomorph__]

LOL long live AMD!!!

 

[10tacle]

Ryzen has its own bugs too with extreme load Linux compiling, but let's be realistic here. What percentage of users out there will ever experience either CPU OEM's bugs in their day to day operations between gaming and productivity apps? My biggest beef with both Skylake and Kaby Lake is their horrible TDP thermals compared to previous generations (especially Kaby Lake). And Ryzen still has memory performance issues getting >2666MHz DDR4 modules up past 2,666MHz on new motherboards without a BIOS fix, and not all of them have it yet.

I hope Intel gets it right for the delayed 8th-generation Coffee Lake and Z370 chipset next year.

 

[hannibal]

Yep. Every processor has bugs. It is just how and when they will be corrected.

 

[bloodroses]

Yep. Every processor has bugs. It is just how and when they will be corrected.

Exactly. And as CPUs continue to get more advanced and more efficient in design with heavy deadlines, expect it to become more common. Software has been the same way, but at least that is easily fixed through software. For hardware, the only real way to fix the problem is with workarounds; at least until the day reprogrammable CPUs can compare to dedicated chips for performance.

 

[alextheblue]

Ryzen still has memory performance issues getting >2666MHz DDR4 modules up past 2,666MHz on new motherboards without a BIOS fix, and not all of them have it yet.

To be fair if you're building a high performance rig and you care about such things, you probably should get a premium board from a company that is known to have good support.

 

[bit_user]

For hardware, the only real way to fix the problem is with workarounds; at least until the day reprogrammable CPUs can compare to dedicated chips for performance.

Except the article suggest this is a bug in the microcode, which is software programming and therefore completely fixable with just a BIOS update.

 

[Decends]

Hmm, hope this wont be an issue for my grandma and cousins's new PC i built em using a G4600.

 

[Jasjar]

You won't have any issues, the G4600 doesn't have hyperthreading.

 

[Decends]

You won't have any issues, the G4600 doesn't have hyperthreading.

uh, about that, its a dual core hyperthreaded cpu like the g4560.......

 

[cats_Paw]

WEll, I got a Ryzen 7 1700 and bought Win7 for that system.
It was a major pain to get it to work correctly (took me 2 full days to build and get the system to run).
Yes, problems with PCs always appear, but this issue with intel is bad news in a time when they are facing real competition for the first time in years.

 

[nzalog]

WEll, I got a Ryzen 7 1700 and bought Win7 for that system.
It was a major pain to get it to work correctly (took me 2 full days to build and get the system to run).
Yes, problems with PCs always appear, but this issue with intel is bad news in a time when they are facing real competition for the first time in years.

I guess but the reality of the situation is, it's a bios update to fix and I've been using a kabylake processor (e3-1240-v6) affected by this bug since the release of the processor in busy esxi server and I have not had any issues. I also have another gaming machine affected by this and still no issues. So while sure the news sounds horrible it's seems like a very specific set of conditions have to be met that don't commonly appear in real world use.

 

[Deleted member 1353997]

This may sound weird, but I'm actually happy about this news.

I've been having problems with Windows 10 hanging almost every day ever since I built a new PC with a Skylake i7 6700K CPU. Despite tons of researching, I never found an explanation for this weird problem, not to mention a solution.

This news is the first time since long that I've seen something that might be related to my issue. Just thinking that I may finally be able to solve my problem by disabling HT fills me with joy.
It sucks, but disabling HT is significantly better than buying a new mainboard and CPU.

No, this is very likely not your issue.

Ok, so it's been 2 days since I disabled HT, and I haven't experienced the problem since.
Considering my PC had been freezing every day, sometimes multiple times a day, I'd say 2 days without problems is a good sign.

But just for the record (and in case my problem hasn't been fixed after all), why do you think that HT bug is likely not my issue?

 

[nzalog]

This may sound weird, but I'm actually happy about this news.

I've been having problems with Windows 10 hanging almost every day ever since I built a new PC with a Skylake i7 6700K CPU. Despite tons of researching, I never found an explanation for this weird problem, not to mention a solution.

This news is the first time since long that I've seen something that might be related to my issue. Just thinking that I may finally be able to solve my problem by disabling HT fills me with joy.
It sucks, but disabling HT is significantly better than buying a new mainboard and CPU.

No, this is very likely not your issue.

Ok, so it's been 2 days since I disabled HT, and I haven't experienced the problem since.
Considering my PC had been freezing every day, sometimes multiple times a day, I'd say 2 days without problems is a good sign.

But just for the record (and in case my problem hasn't been fixed after all), why do you think that HT bug is likely not my issue?

Hyper-threading is one of the things you can turn off to make overclocks stable. Is you computer crashing at stock speeds? (If it doesn't crash stock then you're overclocked too high) How about below stock speeds? (If underclocking fixes the issue, your CPU is damaged). Because if it was this bug it would not make any difference what speed you ran it on. It is quite possible that some piece of software you installed maybe is doing this very specific task but unlikely.

 

[Deleted member 1353997]

Hyper-threading is one of the things you can turn off to make overclocks stable. Is you computer crashing at stock speeds? (If it doesn't crash stock then you're overclocked too high) How about below stock speeds? (If underclocking fixes the issue, your CPU is damaged). Because if it was this bug it would not make any difference what speed you ran it on. It is quite possible that some piece of software you installed maybe is doing this very specific task but unlikely.

As far as I know, my PC is not overclocked. I did try overclocking the CPU a bit once, but since the temperature increased too much, I immediately reset it to stock speeds.

So, I tried re-enabling HT and underclocking the CPU, the problem came back.
The funny thing is, my PC never experiences this issue when under load. I can play games or encode video streams for hours without any problems. I've only ever witnessed the problem happening when the PC is idle. It might be just coincidence, or maybe something in the background is putting load on the CPU and I don't know about it.


On a related note: I decided to read about the problem in more detail by reading the mailing list that described the bug. According to it, Intel already knew about the bug and released a fix to its partners in April this year. So I went to look for a BIOS update, and found one released in late April that "improves system stability".
I've installed the BIOS update and left HT on. My PC hasn't crashed yet which is a good sign, but since the issue can take hours to manifest I'm going to observe it a bit longer.

 

[bit_user]

I've installed the BIOS update and left HT on. My PC hasn't crashed yet which is a good sign, but since the issue can take hours to manifest I'm going to observe it a bit longer.

If that fixes it, I'd be curious to know if you have any devices installed that would require special drivers (like TV capture devices, RAID cards, etc.), or have basically any other software that's running all the time (like anti-virus).

 

[Deleted member 1353997]

If that fixes it, I'd be curious to know if you have any devices installed that would require special drivers (like TV capture devices, RAID cards, etc.), or have basically any other software that's running all the time (like anti-virus).

I have a RAID setup, but not using a RAID card.
I don't have an anti-virus, just Windows Defender.

The most specialized hardware I have is a Logitech G19 keyboard with LCD screen.
I'm also using AIDA64 to feed that LCD screen with monitoring data, like CPU load/temperature, and similar.
Other permanently running software include Steam, GOG Galaxy, the Blizzard Launcher, NVIDIA Capture Server Proxy (for ShadowPlay), Realtek HD Audio Manager, OneDrive, and AMD Dual-Core Optimizer (not sure why, but it's there).

I doubt those were responsible for the freezes, as I've been using them for years without any issues on a PC with i7 3770K.
The issues only appeared ever since I built a new PC with i7 6700K. At first I thought the issue was because of a bug in Windows 10, but since none of the other Windows 10 PCs I've used had that issue, I had a feeling it might be because of my hardware. Since all I could see was "Windows did not shut down properly", I had absolutely no clue how to fix it. I tried to update my BIOS and I even followed some of the most unlikely fixes including reinstalling network drivers and running checkdisk without any success.
That's why I'm glad I saw this article, it gave me another lead, and I even managed to fix my problem.

PS: So I've re-enabled HT and installed that new BIOS from April (the one released after Intel had supposedly fixed their HT bug). I still haven't encountered the problem. I think it's pretty obvious now that my freezing issue was related to the HT bug.

 

[bit_user]

I doubt those were responsible for the freezes, as I've been using them for years without any issues on a PC with i7 3770K.

Well, if you're right that this was the hyperthreading bug you experienced, then a piece of software which satisfied the conditions to trigger the bug would run fine on the i7-3770K (which lacked the bug) and fail on your Skylake. So, this actually supports your case.

 

[dE_logics]

And before any Windows user thinks that it's a bug with Intel rather than their beloved Windows PC -- no it's a bug/security vulnerability with Windows your favorite virus/spyware/malware/ransomware/worm etc... etc... etc... does not exploit your 'PC' because of this errata, it's because your window(s) is flawed.

You'll need more than big beautiful and shiny buttons to trigger this bug.

 

[Hernan_5]

Can this cause random reboots?