Disable hyper-threading on Intel Skylake & Kaby Lake CPU

In 4½ months I have experienced 16 BSOD system crashes on a new work computer:

Crash Date Bug Check String Bug Check Code Caused By Address
21-06-2017 DRIVER_POWER_STATE_FAILURE 0x0000009f ntoskrnl.exe+70e40
12-06-2017 NTFS_FILE_SYSTEM 0x00000024 Ntfs.sys+4211
23-05-2017 IRQL_NOT_LESS_OR_EQUAL 0x0000000a ntoskrnl.exe+6f4c0
10-05-2017 IRQL_NOT_LESS_OR_EQUAL 0x0000000a ntoskrnl.exe+6f440
01-05-2017 BAD_POOL_HEADER 0x00000019 win32k.sys+f13b2
24-03-2017 BAD_POOL_CALLER 0x000000c2 ntoskrnl.exe+6f440
17-03-2017 SYSTEM_SERVICE_EXCEPTION 0x0000003b afd.sys+41448
14-03-2017 MEMORY_MANAGEMENT 0x0000001a ntoskrnl.exe+70400
13-03-2017 PAGE_FAULT_IN_NONPAGED_AREA 0x00000050 VBoxDrv.sys+1f037
10-03-2017 PFN_LIST_CORRUPT 0x0000004e ntoskrnl.exe+70400
02-03-2017 SYSTEM_SERVICE_EXCEPTION 0x0000003b ntoskrnl.exe+70400
22-02-2017 BAD_POOL_CALLER 0x000000c2 TDI.SYS+10be
17-02-2017 BAD_POOL_HEADER 0x00000019 ntoskrnl.exe+70400
16-02-2017 SYSTEM_THREAD_EXCEPTION_NOT_HANDLED 0x1000007e iusb3xhc.sys+7dfb0
08-02-2017 PAGE_FAULT_IN_NONPAGED_AREA 0x00000050 ntoskrnl.exe+70400
07-02-2017 PFN_LIST_CORRUPT 0x0000004e ntoskrnl.exe+70400


Until now I have:

  • Performed multiple memory tests.
  • Checked SSD health.
  • Checked system files.
  • Examined multiple memory dumps with WinDbg.
  • Installed all relevant firmware and driver updates.
  • Scanned for malware.


However this has not been successful or revealed the real cause behind the problems.


I eventually decided to replace the original memory modules:

2 x 8 GB DDR4-2133 CL15, Kingston KVR21N15D8K2/16


2 x 8 GB DDR4-2133 CL15, Crucial CT8G4DFS8213.C8FDR1


This seemed to help somewhat.

System crashes used to be a semiweekly event.

After replacing the memory modules it became a semimonthly event.


The system has an Intel Skylake CPU (Core i7-6700)


It has recently been discovered that some Intel Skylake and Kaby Lake CPU’s have a hardware bug related to hyper-threading.

The bug is described in: 6th Generation Intel® Processor Family – Specification Update


“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 (e.g. RAX, EAX or AX for AH) may cause unpredictable system behavior. This can only happen when both logical processors on the same physical processor are active.”


Until system vendors include microcode fixes in firmware/UEFI updates, the only workaround is to disable hyper-threading.


The stability problems I have experienced could be caused by this CPU hardware bug.

So I have disabled hyper-threading in BIOS/UEFI setup and will await firmware updates. I hope that the system will finally be stable and reliable.


If you have an Intel Skylake or Kaby Lake CPU, it is recommend to disable hyper-threading for now.