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Windows 10 (1709) Kernel Power Error 41 when writing to encrypted drives.

2018-01-14
2018-01-22
  • Krister Stålhandske

    I recently upgraded my PC with a new motherboard , CPU and RAM and made a clean install of Windows 10 Pro version 1709 on an internal SSD drive.
    I have two encrypted hdd's, one is internal sata and the other is an external USB, they are both non-system drives (.
    I've been using the encrypted drives for a long time on my older hardware and Windows 10 Pro 1703 without any issues, but now when I try to copy files to or from the drives the PC just shuts down after a while, like the power is pulled. I get the Kernel Power error 41 in windows event log (no dump).

    First I thougt it might be a failing MB or bad RAM or something hardware related but I ran some test on the hardware and it seems ok.
    Then I decided to install Windows 7 (on the same PC) on another internal sata drive just to test if the same problem occurs, but it doesn't, I can copy files to and from the encrypted drives without any kernel error or bluescreen.
    So my conclusion is that something in Windows 10 1709 is bad, maybe memory management or similiar.

    Has anyone experienced something like this?

     
  • Kurt Fitzner

    Kurt Fitzner - 2018-01-14

    To be clear, the computer actually shuts off?

    This is almost certainly a hardware issue. Without going into some really low level guts of a computer's EC firmware in a very brand-specific-way, this isn't even possible to do in software. It is possible your EC firmware is misbehaving due to some aspect of Windows 10 1709, but I would be surprised if VeraCrypt was involved in any way except maybe just as a source of CPU/power stress. VeraCrypt can expose latent issues more quickly, simply because it couples high disk activity with high CPU usage (when high disk activity normally means less CPU activity) and also uses CPU instructions which are uncommonly used elsewhere (AES-NI, for example). Any issues with a CPU's microcode or the computer's power rail can sometimes be exposed with VeraCrypt when nothing else will.

    I know this is little practical help. I wish I could be more help. I have run into many issues where VeraCrypt was involved, but this doesn't feel like one of them.

     
  • Krister Stålhandske

    Yes the computer shuts off and reboots, like pressing the reset button.

    I also was certain it was a hardware fault in the beginning.
    Then I installed Windows 7 on a separate drive on the same computer and booted up on it, mounted the encrypted drives and did several read and write test by copying files to and from the drives without any issues, so I'm no longer sure if it's hardware related. Wouldn't there be same kind of CPU/power stress in Win 7 as in Win 10?

    I'm thinking of decrypting one or both drives in Win 7 just to see if they work in Win 10 without encryption.

     

    Last edit: Krister Stålhandske 2018-01-15
  • Krister Stålhandske

    Ok, here's a little update on the subject.

    I've been doing a lot of testing to figure out what's causing the reboots.
    I've tested each stick of RAM in different slots, made no difference.
    I have run memtest86 for several hours without any errors.
    Run all Prime95 torture tests without any errors.
    Run sfc /scannow, chkdsk and so on without any issues.
    Scanned hdd's for virus, all clean.
    Win 10 is still rebooting after a while when copying files to or from or between the encrypted drives.

    and....

    I've booted up on the Windows 7 hdd and been copied files approx 500Gb worth of data to the encrypted drives without any issues, no rebooting, no BSOD, it just works like a charm.

    So...

    I'm 99.9% sure it's not faulty hardware and I'm 99,9% sure it's something fubar in Windows 10 1709 code and not in Veracrypt.
    I might be the only one having these troubles with Veracrypt encrypted drives but after doing some research I can see that there is a lot of people having all sorts of trouble with Win 10 1709, like spontaneous reboots, PC freezing, stuttering in games and BSOD.

    I hope that the next big version update of Win 10 will solve all these issues, because this sucks.

     

    Last edit: Krister Stålhandske 2018-01-18
    • Mounir IDRASSI

      Mounir IDRASSI - 2018-01-18

      Thank you for your tests and this detailed feedback.

      The Kernel Power error 41 is a low level system error that can not be caused directly by software (it even escapes Windows own crash handler). This error is often the symptom of a device power failure.
      Since in your case, Windows 7 is working properly on the same, your conclusion that this is specific to Windows 10 1709 is correct but it can be the fault of a device driver that doesn't implement correctly some new changes in build 1709 especially those related to power management (I don't know if you already tried changing the advanced power configuration in Windows).

       
  • Krister Stålhandske

    Thanks for the reply!
    I am running the high performance settings and I have disabled fast startup.
    When you say device driver, are there any specific device or driver I should check? (considering the fact that writing to the encrypted drives seems to trigger the fault much faster and more frequently then just reading from them)

     

    Last edit: Krister Stålhandske 2018-01-18
  • Krister Stålhandske

    Today I changed the power scheme from "High Performance" to "Balanced" which is the recommended scheme by Microsoft.
    The result was the same, PC reboots after a while when copying files to encrypted drives.
    I'm lost....

     
  • Krister Stålhandske

    OK, I think I've found the culprit!

    I went through the BIOS settings and noticed that "Intel Turbo Boost" was enabled.
    After I disabled it I have'nt managed to reproduce the problem in Win 10 anymore (fingers crossed).

    I'm still wondering why does everything work flawlessly in Win 7 with this "Turbo boost" enabled and not in Win 10?

    BTW.
    I'm kind of happy...... ;-)

     
  • Mounir IDRASSI

    Mounir IDRASSI - 2018-01-20

    Thank you Krister for the update.
    I expected the issue to be on driver side of disk or controller but it is difficult to know for sure (even Windows doesn't know!).

    I never thought that Intel Turbo Boost would fix the issue. Basically, disabling it reduces CPU speed during peak of operations, which is the case of VeraCrypt encryption. So, maybe the issue with the CPU itself (or its microcode loaded by Windows) or just that reducing CPU speed hides the original problem.

    Does your CPU provide AES-NI? If yes, are you using AES as the only encryption algorithm?
    It would be intersting to know if the error happens or not when AES-NI is used exclusively since it has a dedicate unit in the CPU.

     
  • Krister Stålhandske

    Yes the CPU provides AES-NI, it's an Intel i7 7700K 4.2GHz and the motherboard is ASUS Strix Z270H Gaming.
    Both encrypted drives uses AES as encryption algorithm.
    In Veracrypt I have AES hardware acceleration enabled, (I have tested AES hardware acc disabled earlier in my search and that did'nt help) I also did a lot of benchmark in Veracrypts driver conf windows without any issues.
    What do you mean with "AES-NI is used exclusively"?

    If there would be an issue within the CPU itself wouldn't the same problem occur in Win 7?
    It's more likely Win 10 1709 micro code vs BIOS code. I've tried both with and without Microsofts "Spectre/Meltdown" security patch and that didn't make any difference. I also tried the latest BIOS with the "Intel bug" fix, that didn't solve the problem (I later reverted back to the older BIOS because of RAM stability issues).

    Watching CPU load in windows task managers performance tab, it never spikes it just utilizes 1-10% of CPU and the CPU speed doesn't go above 3GHz when copying. The disk drive activity is sometimes 100%.

     
  • Krister Stålhandske

    Time to report in again...

    I'm now pretty sure that it's not Intels Turbo Mode itself that's the problem but Turbo Mode in combination with "Asus Multi Core Enhancement" enabled in BIOS.
    I have now done some testing with Turbo Mode enabled and "Asus Multi Core Enhancement" disabled and I haven't had any crashes yet....

     

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