Rubin Shrestha
Rubin Shrestha
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Windows 10 IoT LTSC: UWF enabled causes massive boot delay when NO USB mouse is connected

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Environment

  • OS: Windows 10 IoT Enterprise LTSC 2021 (build 19044.x)
  • UWF: Enabled, protecting C: only
  • Overlay: RAM overlay, max 1024 MB, persistent = OFF
  • Fast Startup: Disabled (same state for all tests)

Problem summary

I have a Windows image using Unified Write Filter (UWF) on C:. Boot time behavior changes drastically depending on whether a USB mouse is present at power-on:

  • UWF OFF: boots ~1:40 (mouse present or not)
  • UWF ON + USB mouse plugged in: boots ~1:40
  • UWF ON + NO USB mouse plugged in: boots anywhere from ~4:25-30:00 (slow/hangs at Windows logo/spinner stage, then eventually reaches desktop)

The delay only occurs when:

UWF is enabled AND no USB mouse is connected

Current UWF configuration

Unified Write Filter Configuration Utility version 10.0.19044
Copyright (C) Microsoft Corporation. All rights reserved.

Current Session Settings


FILTER SETTINGS
    Filter state:     ON
    Commit pending:   NO
    Shutdown pending: NO
    HORM mode:        OFF

SERVICING SETTINGS
    Servicing State: OFF

OVERLAY SETTINGS
    Type:                  RAM
    Maximum size:          1024 MB
    Warning Threshold:     512 MB
    Critical Threshold:    1024 MB
    Read Only Media:       OFF
    Freespace Passthrough: OFF
    Persistent:            OFF
    Reset Mode:            N/A
    Reset Saved Mode:      N/A



VOLUME SETTINGS
Volume 3ae845b3-0000-0000-0000-100008000000 [D:]
    Volume state:     Un-protected
    Volume ID:        3ae845b3-0000-0000-0000-100008000000
    Swapfile:         0 MB

    File Exclusions:
Current Session Exclusions for Volume 3ae845b3-0000-0000-0000-100008000000 [D:]
        *** No exclusions

Volume 3ae845b3-0000-0000-0000-100000000000 [F:]
    Volume state:     Un-protected
    Volume ID:        3ae845b3-0000-0000-0000-100000000000
    Swapfile:         0 MB

    File Exclusions:
Current Session Exclusions for Volume 3ae845b3-0000-0000-0000-100000000000 [F:]
        *** No exclusions

Volume 3927594f-0000-0000-0000-100000000000 [C:]
    Volume state:     Protected
    Volume ID:        3927594f-0000-0000-0000-100000000000
    Swapfile:         0 MB

    File Exclusions:
Current Session Exclusions for Volume 3927594f-0000-0000-0000-100000000000 [C:]
    C:Program Files (x86)NTPetcntp.drift
    C:Temp
    C:DC
    C:WindowsFBShell.ini
    C:WindowsHMIStatus.ini
    C:WindowsFBFirstBoot.ini
    C:FB20cfgRouterConfigs
    C:FB20cfgRoutingConfigs



REGISTRY EXCLUSIONS
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlTimeZoneInformation
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionTime Zones
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass{4d36e972-e325-11ce-bfc1-08002be10318}
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersInterfaces
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlNsi
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersion
    HKEY_LOCAL_MACHINESOFTWAREWOW6432NodeMicrosoftWindows NTCurrentVersion
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32Time
    HKEY_LOCAL_MACHINESYSTEMMountedDevices

Next Session Settings


FILTER SETTINGS
    Filter state:     ON
    Commit pending:   N/A
    Shutdown pending: N/A
    HORM mode:        N/A

SERVICING SETTINGS
    Servicing State: OFF

OVERLAY SETTINGS
    Type:                  RAM
    Maximum size:          1024 MB
    Warning Threshold:     512 MB
    Critical Threshold:    1024 MB
    Read Only Media:       OFF
    Freespace Passthrough: OFF
    Persistent:            OFF
    Reset Mode:            N/A
    Reset Saved Mode:      N/A



VOLUME SETTINGS
Volume 3ae845b3-0000-0000-0000-100008000000 [D:]
    Volume state:     Un-protected
    Volume ID:        3ae845b3-0000-0000-0000-100008000000
    Swapfile:         0 MB

    File Exclusions:
Next Session Exclusions for Volume 3ae845b3-0000-0000-0000-100008000000 [D:]
        *** No exclusions

Volume 3ae845b3-0000-0000-0000-100000000000 [F:]
    Volume state:     Un-protected
    Volume ID:        3ae845b3-0000-0000-0000-100000000000
    Swapfile:         0 MB

    File Exclusions:
Next Session Exclusions for Volume 3ae845b3-0000-0000-0000-100000000000 [F:]
        *** No exclusions

Volume 3927594f-0000-0000-0000-100000000000 [C:]
    Volume state:     Protected
    Volume ID:        3927594f-0000-0000-0000-100000000000
    Swapfile:         0 MB

    File Exclusions:
Next Session Exclusions for Volume 3927594f-0000-0000-0000-100000000000 [C:]
    C:Program Files (x86)NTPetcntp.drift
    C:Temp
    C:DC
    C:WindowsFBShell.ini
    C:WindowsHMIStatus.ini
    C:WindowsFBFirstBoot.ini
    C:FB20cfgRouterConfigs
    C:FB20cfgRoutingConfigs



REGISTRY EXCLUSIONS
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlTimeZoneInformation
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionTime Zones
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass{4d36e972-e325-11ce-bfc1-08002be10318}
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersInterfaces
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlNsi
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersion
    HKEY_LOCAL_MACHINESOFTWAREWOW6432NodeMicrosoftWindows NTCurrentVersion
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32Time
    HKEY_LOCAL_MACHINESYSTEMMountedDevices

What I’ve already tried

  • Added the HID/USB-related registry exclusions (EnumUSB, EnumHID, DeviceClasses, etc.).
  • Confirmed the slowdown still happens only in the no-mouse + UWF enabled case.
  • Avoided broad exclusions like entire HKLMSYSTEM or HKLMSOFTWARE because I don’t want to destabilize the system.

Questions

What specific registry keys and/or file paths are typically responsible for this kind of “boot slows/hangs only when no USB HID device is present” behavior under UWF?

How can I prove whether or not this issue is related to a missing registry exclusion vs a missing file/directory exclusion?

Goal

Keep C: protected with UWF, but have consistent boot time (~1:40) regardless of whether a USB mouse is connected.

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