Posted on 06/26/2017 9:37:28 AM PDT by Ernest_at_the_Beach
Dark side of the hyperthreading loom
While the war is blazing between Intel and AMD fanboys over the superiority of the latest range of chips, Debian developers have spotted some rather nasty coding in Chipzilla’s latest creations.
During April and May, Intel started updating processor documentation with a new errata note and it turned out that the reason was that Skylake and Kaby Lake silicon has a microcode bug it did not want any one to find out about.
The errata is described in detail on the Debian mailing list, and 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.
According to the Debian advisory says affected users need to disable hyper-threading “immediately” in their BIOS or UEFI settings, because the processors can “dangerously misbehave when hyper-threading is enabled”.
Symptoms can include application and system misbehaviour, data corruption, data loss and voting Donald Trump. We made the last one up.
Henrique de Moraes Holschuh warned that all operating systems, not only Linux, were subject to the bug.
Intel said that 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 behaviour.
“This can only happen when both logical processors on the same physical processor are active.”
It might never have been noticed if Mark Shinwell, a developer working on the OCamlL toolchain, had not contacted the Debian team to explain that the OCaml compiler triggered an Intel microcode issue.
Debian's post notes that Intel has documented the bug and its microcode fixes for Core 6th generation, Core 7th generation, Xeon v5 and v6, and Core 6th generation X series. Mostly this depends on vendors providing BIOS/UEFI updates. However, until they do that, it would be to disable hyper-threading or even shift to AMD.
I remember when Sr Managers at Intel were forced to outsource CPU validation to Costa Rica.
These things never happened back 10 years ago.
Other than the FPU flaw which was covered up by an Executive from India.
And Debian gave more detail.
Earlier post:
Debian Project Warns: Turn off Hyperthreading with Skylake and Kaby Lake (Ubuntu affected)
Tech post with the obligatory anti-Trump snark...
They just blew their credibility out the water............
This does not bode well for Intel.
One of the reasons people are willing to pay more Intel chips
are dependability and flawless performance.
Another door for AMD has just opened.
Oh, is that all? As if you could just run down to your local Best Buy, grab an AMD chip, and swap the processors. Sure - I'll get right on that.
My prior snarky comment aside, this is not only right, but the timing is excellent for AMD as their new chip line has just rolled out.
Related useless trivia:
For desktop cpus, Intel Core i3 and Core i7 cpus utilize hyperthreading.
Intel Core i5 cpus do not have hyperthreading, although Core i5 cpus are generally faster and more powerful than i3 cpus because they have more real cores (hyperthreading adds virtual cores).
For example, my desktop computer has an Intel Skylake i5-6500 which has 4 cores but no hyperthreading. Despite this, benchmark testing shows that the i5 is faster and more powerful than the i3 skylakes because the i3 come with just two real cores.
Easy for me to say since I am not working with designs nor have I ever.
I just worried about installed the Old big iron,.
It’s an English freaky tech website.
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06-25-2017, 01:49 PM
Ping.
Thanks to upchuck for the ping!!
This is really only a necessary precaution if you are running these CPU’s on critical up-time infrastructure like web or database servers.
A Bios update fixes the problem.
Just did mine.
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