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Intel has shipped Hyper-Threading CPUs for well over a decade, even subtracting the Cadre 2 era when the technology wasn't used. For near of that time, Hyper-Threading has been a engineering that 'just worked.' Initial problems under Windows 2000 and Windows XP were ironed out by service packs and software updates. And while there's been the very occasional case in which turning off Hyper-Threading improves operation, it's a rare enough issue that I tin't recall any instances offhand.

Now, a major Hyper-Threading flaw has been discovered that tin can destabilize Intel CPUs based on both Kaby Lake and Skylake — not something Intel needed on the heels of AMD's new CPUs. The effect is reported to cause "unpredictable arrangement behavior," which could mean annihilation from corrupting data to outright system crashes. The effect was picked up by Hot Hardware, via Debian.org. While Debian is a Linux distro, the warning makes it articulate that the problem can happen to whatever operating system and is not limited to Linux.

The Debian warning page gives extensive data on how to place which CPU you're using and how to utilise a gear up (at to the lowest degree, where fixes are available). As of this writing, in that location are two ways to fix the trouble. The first, and most obvious, is to disable Hyper-Threading birthday.

Hyper-Threading

Hyper-Threading is generally a positive for Intel chips.

The second is to wait for your motherboard vendor to push a new UEFI version. The Debian page notes: "Yous want your organisation vendor to provide a BIOS/UEFI update that fixes "Intel processor errata KBL095, KBW095 or the like ane for my Kaby Lake processor".

Skylake users, meanwhile, demand a UEFI that addresses "Intel erratum SKW144, SKL150, SKX150,
SKZ7, or the similar ane for my Skylake processor."

The Problem in Detail

Here's how Intel describes the errata in its own documentation.

Errata: SKZ7/SKW144/SKL150/SKX150/SKZ7/KBL095/KBW095 Short Loops Which Utilise AH/BH/CH/DH Registers May Crusade Unpredictable System Beliefs.

Problem: Under complex micro-architectural weather, brusk loops of less than 64 instructions that use AH, BH, CH or DH registers too as their corresponding wider register (eastward.one thousand. RAX, EAX or AX for AH) may cause unpredictable system beliefs. This can only happen when both logical processors on the same concrete processor are active.

Implication: Due to this erratum, the arrangement may experience unpredictable system behavior.

Intel has plainly issued microcode updates for Skylake and Kaby Lake processors to accost this problem, simply they'll demand to be integrated into motherboard UEFI to work finer. Nosotros recommend checking for board updates to see if there's an update available if y'all're using a Skylake or Kaby Lake flake.

For the record, while ExtremeTech believes Intel that these errata exist, we are not aware of whatsoever software programs affected past them and have not observed any bug with our Skylake or Kaby Lake testbeds. Our Core i7-7700K and Core i7-6700K both performed flawlessly when tested in our benchmark suites over the past six months.

If you're having a specific problem with a slice of software that cropped up once you moved to Kaby Lake or Skylake, we recommend shutting off Hyper-Threading and seeing if that resolves the problem. Hopefully motherboard manufacturers volition take solutions ready to go sooner rather than later.

Now read: Intel Core i5 vs. Cadre i7: Which processor should you lot purchase?