Windows Stop Code 0x0000003E: MULTIPROCESSOR_CONFIGURATION_NOT_SUPPORTED

Quick Answer

MULTIPROCESSOR_CONFIGURATION_NOT_SUPPORTED (0x0000003E) means Windows detected multiple processors that are asymmetric in a way it does not support. Microsoft describes the documented cause as processors of different types or levels being used together. No bug-check parameters are defined for this code. Microsoft Learn

Start by checking the processor configuration against the computer or server manufacturer’s requirements, particularly after a CPU replacement or upgrade. If the installed configuration appears supported, collect the processor inventory, firmware information, and any crash dump for further investigation.

What the Error Means

Microsoft’s description concerns compatibility among the processors presented to Windows. Its historical example involves two different processor types installed together. The error does not identify which processor must be replaced or establish that a processor is physically defective. Microsoft Learn

For current systems, follow the exact model’s processor support and population rules. For example, Dell’s guidance for the referenced Intel Xeon Scalable PowerEdge platforms calls for identical CPUs in a system with multiple sockets. This is platform-specific guidance; confirm the requirements for your own machine. Dell Technologies Info Hub

A Note About Modern Hybrid Processors

Some modern processors intentionally combine different core types. Intel’s performance hybrid architecture, for example, includes Performance-cores and Efficient-cores within one processor. Their presence alone is not evidence of an unsupported CPU configuration. Check the supported combination of processor, motherboard, firmware, and operating system. intel.com

Before You Begin

• Record the exact stop code and when it first appeared.
• Note recent CPU replacements, motherboard changes, firmware updates, or virtual machine configuration changes.
• Back up important data and document the current configuration.
• Plan downtime before hardware or firmware work.
• Have the system’s service manual and recovery information available.
• Use a qualified technician for processor removal or installation.

Hardware precaution: Processor servicing requires the manufacturer’s shutdown, power-disconnection, cooling, and electrostatic-discharge procedures. Do not remove a CPU merely to test a guess.

Recommended Troubleshooting

1. Identify What Changed

Use the timing of the first crash to prioritize the investigation.

The firmware and virtual-machine checks above are investigation steps. Microsoft’s 0x3E page does not list them as confirmed causes.

2. Record the Installed Processors

If Windows starts, open PowerShell and run this read-only command:

Get-CimInstance -ClassName Win32_Processor |
    Select-Object DeviceID, SocketDesignation, Name, Manufacturer,
        NumberOfCores, NumberOfLogicalProcessors

This displays processor identification, socket labels, and core counts reported through Windows Management Instrumentation. It does not change the system. Microsoft documents Win32_Processor and using Get-CimInstance to retrieve processor information. Microsoft Learn

Compare the results with the system’s inventory and service documentation. Matching display names alone do not establish that a processor combination meets every platform requirement.

If Windows cannot start, obtain the inventory from firmware setup, the server’s management interface, or service records. Record exact processor models and part numbers where available.

3. Check the Platform’s Compatibility Rules

Consult the manufacturer’s documentation for the exact system or motherboard model. Verify:

• Supported processor models.
• Rules for combining processors across sockets.
• Required firmware versions.
• Processor installation and socket-population requirements.

If the problem began immediately after a CPU upgrade, have a technician verify the replacement part and restore the previous supported configuration where appropriate.

Dell’s identical-CPU requirement is an example of why matching the socket or processor family alone is insufficient. Dell Technologies Info Hub

4. Review Firmware or Virtual Machine Changes

If a firmware change preceded the error, consult the hardware vendor before updating again or downgrading. Follow its exact procedure and recovery guidance.

Firmware precaution: Record existing settings and confirm the correct update package before proceeding. An interrupted or unsuitable firmware update can prevent startup.

For a virtual machine, ask the virtualization administrator to review the virtual CPU configuration and any recent migration or compatibility-setting changes. Preserve the existing configuration before changing it. A reduction to one virtual CPU is not a documented universal repair for 0x3E.

Advanced Troubleshooting

If the processor configuration is supported and the error continues, provide support personnel with:

• Computer or server model.
• Installed processor models and part numbers.
• BIOS or UEFI version.
• Windows version and build.
• Recent hardware or configuration changes.
• Available crash dumps.

When Windows successfully writes a dump, small dumps normally appear in %SystemRoot%\Minidump; several larger dump types use %SystemRoot%\MEMORY.DMP.

An IT professional can open the dump in WinDbg and run:

!analyze -v

This displays diagnostic information. It does not repair the configuration, and Microsoft defines no code-specific parameters for 0x3E. learn.microsoft.com

How to Verify the Fix

After correcting a configuration:

1. Start Windows normally.
2. Confirm that the expected processors and cores are recognized.
3. Verify that the hardware inventory matches the approved configuration.
4. Perform representative workloads and planned restarts.
5. Check whether the same stop code returns.

If the error recurs, retain new diagnostic evidence and escalate to the hardware or virtualization vendor before making further changes.

Frequently Asked Questions

Does this error mean a CPU is defective?

Not necessarily. Microsoft documents a processor compatibility condition. Physical failure requires separate diagnostic evidence. Microsoft Learn

Must processors have identical clock speeds?

Clock speed alone is not a sufficient compatibility check. Follow the system manufacturer’s complete CPU-matching requirements. The referenced Dell platforms require identical CPUs. Dell Technologies Info Hub

Do Performance-cores and Efficient-cores cause this error automatically?

No. Different core types are an intentional feature of supported hybrid processors. Their presence alone does not diagnose bug check 0x3E. intel.com

Will reinstalling Windows correct an incompatible CPU combination?

Reinstallation does not change the installed processor combination. Verify hardware compatibility first.

Should I disable cores or change Windows processor limits?

Microsoft does not document those changes as a general fix for 0x3E. Use the platform’s supported configuration and obtain vendor guidance before altering processor settings.

Conclusion

For stop code 0x0000003E, prioritize processor compatibility and recent configuration changes. Verify the complete platform requirements, correct any unsupported combination, and collect diagnostic evidence if the configuration is already supported.

Sources

• Microsoft Learn — Bug Check 0x3E: MULTIPROCESSOR_CONFIGURATION_NOT_SUPPORTED.
• Dell Technologies — Identical CPU and DIMM parts.
• Microsoft Learn — Win32_Processor class.
• Microsoft Learn — Collecting information about computers.
• Intel — What Is Performance Hybrid Architecture?.
• Intel — Performance Hybrid Core Architecture of Intel Core Platform Using Windows.
• Microsoft Learn — Stop code error or bug check troubleshooting.