Bug Check 0xC8: IRQL_UNEXPECTED_VALUE

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.

Important 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.

IRQL_UNEXPECTED_VALUE Parameters

Parameter Description

1

The value of the following bit computation:

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

2

Zero, or APC->KernelRoutine

3

Zero, or APC

4

Zero, or APC->NormalRoutine

You can determine "UniqueValue" by computing (Parameter 1 AND 0xFF). If "UniqueValue" is either zero or one, Parameter 2, Parameter 3, and Parameter 4 will equal the indicated APC pointers. Otherwise, these parameters will equal zero.

Cause

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.