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ERROR_BAD_MCFG_TABLE
device resources conflict with the firmware mcfg table.
ERROR_BAD_MCFG_TABLE means that this condition The ACPI MCFG table describes PCI Express enhanced configuration-space regions. Windows detected that resources required by a device overlap or disagree with those firmware declarations, making direct configuration-space access unsafe.
Where the result appears
- PCI Express device enumeration during boot.
- chipset or bus-driver initialization.
- firmware updates that alter PCIe resource windows.
- virtual machines or unusual platforms presenting an invalid ACPI layout.
What the result tells you
The value identifies a specific Windows state, but it does not by itself identify the component that introduced that state. Preserve the original this result value, the API or subsystem that produced it, and the object being operated on. A wrapper that replaces it with a generic exception or Boolean failure removes the distinction needed to choose the correct recovery path.
Diagnostic evidence to collect
- the MCFG entries, base addresses, segment groups, and bus ranges.
- the conflicting device resources from Device Manager or SetupAPI logs.
- system model, BIOS/UEFI revision, and chipset driver version.
- whether the problem appeared after firmware, hypervisor, or hardware changes.
Correlate the result evidence on one timeline. The first event that changes the state associated with this result is usually more valuable than later retries returning the same code. Record process and thread identity, session, timestamp, API parameters, and the immediately preceding successful operation.
Handling and recovery
Update the system firmware and chipset components from the platform vendor. Restore default firmware settings, remove recent PCIe hardware to isolate the conflict, and provide ACPI tables to the vendor if the platform still publishes an invalid map. Application retries cannot correct firmware resource descriptors.
Retry after this result only when the evidence shows that an external condition can change. When it is caused by malformed input, revoked authority, unsupported state, hardware damage, or an offline maintenance requirement, an unchanged retry adds noise and can overwrite the earliest useful diagnostics.
Common misinterpretation
This is not a malformed application configuration file. MCFG is an ACPI firmware table used for PCI Express configuration access.
Guidance for developers
Keep it in its Win32/LRESULT domain in structured telemetry. When converting it to an HRESULT, exception, RPC response, or JSON field, retain the source domain and numeric value alongside the human-readable text. Do not branch on the localized message string for it.
A it test should construct the specific state, assert the exact result, and verify that partial resources are released. The recovery test for it should prove that the operation is either deferred until a measurable state change or fails without an uncontrolled retry loop.
References
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