The IRQL_UNEXPECTED_VALUE bug check has a value of 0x000000C8. This indicates that the processor's IRQL is not what it should be at this time.


This topic is for programmers. If you are a customer who has received a blue screen error code while using your computer, see Troubleshoot blue screen errors.


Parameter Description


The value of the following bit computation:

(Current IRQL << 16) | (Expected IRQL << 8) | UniqueValue

2 - Depends on UniqueValue

If UniqueValue is 0 or 1: APC->KernelRoutine.

If UniqueValue is 2: the callout routine

If UniqueValue is 3: the interrupt's ServiceRoutine

If UniqueValue is 0xfe: 1 if APCs are disabled

3- Depends on UniqueValue

If UniqueValue is 0 or 1: APC

If UniqueValue is 2: the callout's parameter

If UniqueValue is 3: KINTERRUPT

4 - Depends on UniqueValue

If UniqueValue is 0 or 1: APC->NormalRoutine


This error is usually caused by a device driver or another lower-level program that changed the IRQL for some period and did not restore the original IRQL at the end of that period. For example, the routine may have acquired a spin lock and failed to release it.

The !analyze debug extension displays information about the bug check and can be very helpful in determining the root cause.

See also

Crash dump analysis using the Windows debuggers (WinDbg)

Analyzing a Kernel-Mode Dump File with WinDbg