Graphics Stability Issues

  • Frozen appearence (short or long period)
  • Flickering

One of the most common stability problems in graphics occurs when a computer “hangs” or appears completely “frozen” while, in reality, it is processing an end-user command or operation. The user typically waits a few seconds and then decides to reboot the computer. The frozen appearance of the computer typically occurs because the GPU is busy processing intensive graphical operations, typically during gameplay. The GPU does not update the display screen, and the computer appears frozen.1530296741-p3dv3-4.jpg

In Windows Vista and later, the operating system attempts to detect situations in which computers appear to be completely “frozen”. The operating system then attempts to dynamically recover from the frozen situations so that desktops are responsive again. This process of detection and recovery is known as timeout detection and recovery (TDR). In the TDR process, the operating system’s GPU scheduler calls the display miniportdriver’s  DxgkDdiResetFromTimeout function to reinitialize the driver and reset the GPU. Therefore, users are not required to reboot the operating system, which greatly enhances their experience.

1530296745-p3dv4-3.jpgThe only visible artifact from the hang detection to the recovery is a screen flicker. This screen flicker results when the operating system resets some portions of the graphics stack, which causes a screen redraw. This flicker is eliminated if the display miniport driver complies with Windows Display Driver Model (WDDM) 1.2 and later. Some legacy Microsoft DirectX applications (for example, those DirectX applications that conform to DirectX versions earlier than 9.0) might render to a black screen at the end of this recovery. The user would have to restart these applications.

This sequence briefly describes the TDR process:

Timeout detection in the Windows Display Driver Model (WDDM)

The GPU scheduler, which is part of the DirectX graphics kernel subsystem (Dxgkrnl.sys), detects that the GPU is taking more than the permitted amount of time to execute a particular task. The GPU scheduler then tries to preempt this particular task. The preempt operation has a “wait” timeout, which is the actual TDR timeout. This step is thus the timeout detection phase of the process. The default timeout period in Windows operating systems is 2 seconds. If the GPU cannot complete or preempt the current task within the TDR timeout period, the operating system diagnoses that the GPU is frozen.

To prevent timeout detection from occurring, hardware vendors should ensure that graphics operations (that is, direct memory access (DMA) buffer completion) take no more than 2 seconds in user scenarios such as productivity and game play.

Preparation for recovery

The operating system’s GPU scheduler calls the display miniport driver’s DxgkDdiResetFromTimeout function to inform the driver that the operating system detected a timeout. The driver must then reinitialize itself and reset the GPU. In addition, the driver must stop accessing memory and should not access hardware. The operating system and the driver collect hardware and other state information that could be useful for post-mortem diagnosis.

Desktop recovery

The operating system resets the appropriate state of the graphics stack. The video memory manager, which is also part of Dxgkrnl.sys, purges all allocations from video memory. The display miniport driver resets the GPU hardware state. The graphics stack takes the final actions and restores the desktop to the responsive state. As previously mentioned, some legacy DirectX applications might render just black at the end of this recovery, which requires the end user to restart these applications. Well-written DirectX 9Ex and DirectX 10 and later applications that handle Device Remove technology continue to work correctly. An application must release and then re-create its Microsoft Direct3D device and all of the device’s objects. For more information about how DirectX applications recover, see the Windows SDK.

Limiting Repetitive GPU Hangs and Recoveries

Beginning with Windows Vista with Service Pack 1 (SP1) and Windows Server 2008, the user experience has been improved in situations where the GPU hangs frequently and rapidly. Repetitive GPU hangs indicate that the graphics hardware has not recovered successfully. In these situations, the user must shut down and restart the operating system to fully reset the graphics hardware. If the operating system detects that six or more GPU hangs and subsequent recoveries occur within 1 minute, the operating system bug-checks the computer on the next GPU hang.

TDR Error Messaging

The operating system also logs the preceding message in the Event Viewer application and collects diagnosis information in the form of a debug report. If the user opted in to provide feedback, the operating system returns this debug report to Microsoft through the Online Crash Analysis (OCA) mechanism.

Timeout Detection and Recovery (TDR) Registry Keys

You can use the following TDR (timeout detection and recovery)-related registry keys for testing or debugging purposes only. That is, they should not be manipulated by any applications outside targeted testing or debugging.

  • TdrLevelSpecifies the initial level of recovery. The default value is to recover on timeout (TdrLevelRecover).
    KeyPath   : registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\GraphicsDrivers
    KeyValue  : TdrLevel
    ValueType : REG_DWORD
    ValueData : 
    TdrLevelOff (0) - Detection disabled 
    TdrLevelBugcheck (1) - Bug check on detected timeout, for example, no recovery.
    TdrLevelRecoverVGA (2) - Recover to VGA (not implemented).
    TdrLevelRecover (3) - Recover on timeout. This is the default value.
  • TdrDelaySpecifies the number of seconds that the GPU can delay the preempt request from the GPU scheduler. This is effectively the timeout threshold. The default value is 2 seconds.
    KeyPath   : registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\GraphicsDrivers
    KeyValue  : TdrDelay
    ValueType : REG_DWORD
    ValueData : Number of seconds to delay. 2 seconds is the default value.
  • TdrDdiDelaySpecifies the number of seconds that the operating system allows threads to leave the driver. After a specified time, the operating system bug-checks the computer with the code VIDEO_TDR_FAILURE (0x116). The default value is 5 seconds.
    KeyPath   : registry
    KeyValue  : TdrDdiDelay
    ValueType : REG_DWORD
    ValueData : Number of seconds to leave the driver. 5 seconds is the default value.
  • TdrTestModeReserved. Do not use.
    KeyPath   : registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\GraphicsDrivers
    KeyValue  : TdrTestMode
    ValueType : REG_DWORD
    ValueData : Do not use.
  • TdrDebugModeSpecifies the debugging-related behavior of the TDR process. The default value is TDR_DEBUG_MODE_RECOVER_NO_PROMPT, which indicates not to break into the debugger.
    KeyPath   : registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\GraphicsDrivers
    KeyValue  : TdrDebugMode
    ValueType : REG_DWORD
    ValueData : 
    TDR_DEBUG_MODE_OFF (0) - Break to kernel debugger before the recovery to allow investigation of the timeout. 
    TDR_DEBUG_MODE_IGNORE_TIMEOUT (1) - Ignore any timeout.
    TDR_DEBUG_MODE_RECOVER_NO_PROMPT (2) - Recover without breaking into the debugger. This is the default value.
    TDR_DEBUG_MODE_RECOVER_UNCONDITIONAL (3) - Recover even if some recovery conditions are not met (for example, recover on consecutive timeouts).
  • TdrLimitTimeSupported in Windows Server 2008 and later versions, and Windows Vista with Service Pack 1 (SP1) and later versions. Specifies the default time within which a specific number of TDRs (specified by the TdrLimitCount key) are allowed without crashing the computer. The default value is 60 seconds.
    KeyPath   : registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\GraphicsDrivers
    KeyValue  : TdrLimitTime
    ValueType : REG_DWORD
    ValueData : Number of seconds before crashing. 60 seconds is the default value.
  • TdrLimitCountSupported in Windows Server 2008 and later versions, and Windows Vista with Service Pack 1 (SP1) and later versions. Specifies the default number of TDRs (0x117) that are allowed during the time specified by the TdrLimitTime key without crashing the computer. The default value is 5.
    KeyPath   : registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\GraphicsDrivers
    KeyValue  : TdrLimitCount
    ValueType : REG_DWORD
    ValueData : Number of TDRs before crashing. The default value is 5.


Troubleshooting Definitions


Hello Captains,
in an effort to support you in resolution of errors that might occur during the download, installation and/or activation phase or your installation is preventing you from using your flightsimulator during start up and normal use, please find here a summary of the FMM (Frequently Made Mistakes…) of error interpretation.

Before we dive into the FMM, first of all some definitions, because then we know what we gonna talk about.

Crash to desktop (CTD)

What is a CTD: a crash to desktop (or CTD) is a computer program crash which is said to occur when a program unexpectedly quits, abruptly taking the user back to the desktop. In this situation the desktop will not crash and down but just runs until YOU stop it.
Usually, the term is applied only to crashes where no error is displayed, hence all the user sees as a result of the crash is the desktop. Many times there is no apparent action that causes a CTD. During normal function, the program may freeze for a shorter period of time, and then close by itself. Also during normal function, the program may become a black screen and play the last few seconds of sound (depending on the size of the data buffer) that was being played repeatedly before it crashes to desktop. Other times it may appear to be triggered by a certain action, such as loading an area. One way to track down the source of CTD for games is to run them in windowed-mode.

Fatal system error

What is: A fatal system error, also known as a system crash, stop error, kernel error, or bug check, is when an operating system halts the moment it reaches a condition where it cannot operate safely. When a bug check is issued a crash dumpfile will be created if the system is configured to create them. This file contains a snapshot of useful low-level information about the system that can be used to debug the root cause of the problem. If the user has enabled it, the system will write an entry to the system event log. The log entry contains information about the bug check (including the bug check code and its parameters) as well as a link which will report the bug to Microsoft and provide the user with prescriptive suggestions if the cause of the check is definitive and well-known.

Application crashes (APPCRASH)

When program files or files within your computer’s registry have become corrupted, this can cause the programs to unexpectedly crash. When a program crashes, you will likely get an Appcrash error. The error message will say “Prepar3d” (or whichever program has crashed) has stopped working” and then list rows of technical information regarding the cause of the crash.

Blue Screen of Death (BSOD)

What is BSOD: The Blue Screen of Death (also known as BSoD or Blue Screen), known officially as a Stop Erroror a bug check, is the error screen displayed by the Microsoft Windows family of operating systems upon encountering a critical error, of a non-recoverable nature, that causes the system to crash. In Windows NT-based operating systems, the Stop error occurs when the kernel, or a driver running in kernel mode, encounters any error from which it cannot recover. This is usually caused by an illegal operation being performed, where the only safe action the operating system can take, is to restart the computer. As a result data may be lost, since the user is not given an opportunity to save any unsaved data to disk. The text on the error screen contains an error code along with four other codes, whose meanings depend on the error code itself, and an error name. Depending on the error code, it may display the memory address at which the problem occurred, together with identifying details of the driver file loaded at that address.


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