Microsoft investigates Windows (KB5029351, KB5029331) Unsupported Processor BSOD crashes

Update: MSI has offered a workaround.

Microsoft is looking into a problem users on the latest Windows 11 and Windows 10 builds are facing. Despite running their systems on supported CPUs, the issue leads to an error wherein the PC crashes with a blue screen of death (BSOD) with an error message that says: "UNSUPPORTED_PROCESSOR". (Microsoft recently updated its support list for both Intel and AMD.)

The tech giant is unsure at the moment if it is an issue with Windows or whether the root cause may be something else. As such, the company has requested feedback via the Feedback Hub app.

On the Windows health dashboard it explains:

Microsoft has received reports of an issue in which users are receiving an “UNSUPPORTED_PROCESSOR” error message on a blue screen after installing updates released on August 22, 2023 (KB5029331) [and KB5029351] and then restarting their device. KB5029331 might automatically uninstall to allow Windows to start up as expected.

If you are experiencing issues, please use Feedback Hub to file a report following the below steps:

1. ​Launch Feedback Hub by opening the Start menu and typing "Feedback hub", or pressing the Windows key + F
2. ​Fill in the "Summarize your feedback" and "Explain in more detail" boxes, then click Next.
3. ​Under the "Choose a category" section, click the "Problem" button, and select "Install and Update" category. Then select "Downloading, installing, and configuring Windows Update” subcategory. Click Next.
4. ​Under the "Find similar feedback" section, select the "Make new bug" radio button and click Next.
5. ​Under the "Add more details" section, supply any relevant detail (Note this is not critical to addressing your issue).
6. ​Expand the "Recreate my problem" box and press "Start recording". Reproduce the issue on your device.
7. ​Press "Stop recording" once finished. Click the "Submit" button.

Browsing through Feedback Hub, it seems that MSI motherboards, mainly from Intel's 600 series (Z690) and 700 series (Z790), are the ones where the issue is infesting the most, though it is possible the problem is there on other OEM motherboards too.

In case you have a board from some other maker, like say Asus, Gigabyte, or ASRock, among others, and experiencing this bug, Microsoft would likely appreciate some feedback about those.