Microcode Revision Mismatch Bluescreen Starting Windows 11 Guest

[Dryne]

I attempted to start my guest to see a Microcode Revision Mismtach bluescreen with my only options to restart that it did automatically.  After restart I am seeing messages from VMWare about clearing 2GB, 4GB, 8GB and etc.

Why would this have mysteriously happened?

[bluefirestorm]

The "clearing 2GB, 4GB, 8GB" messages is harmless. I have seen it before on working VMs. I don't think it has anything to do with the BSOD.

What is the host OS? Is it Linux? If it is Linux, you could check if every core/thread has the same microcode.

cat /proc/cpuinfo | grep microcode

Linux OS can update the microcode without requiring a flash of the host UEFI. Windows can too but don't think it is done as frequently as Linux.

Is the CPU an Intel 12th gen or newer?

[Dryne]

This is a new workstation:

Intel i9 14900K CPU

Windows 11 Professional (latest host updates) and Windows 11 Professional guest (also with latest updates).

My system has the latest BIOS updates when it was built.  There are no newer versions.

 

[bluefirestorm]

There is a problem with 12th/13th gen Intel CPUs that only the e-cores get used and causes very poor performance/very slow VMs. Don't know about 14th gen.

It is possible the e-cores and p-cores have different microcode versions. So if it is trying to boot up with multiple vCPUs with a mix of e-core and p-core maybe that's why the microcode mismatch BSOD come up (and perhaps Windows 11 VM does not have Thread Director capabilities).

The workaround for the 12th/13th gen Intel CPUs is to either
(1) set Power Plan of Windows 10/11 host to High Performance or
(2) disable power throttling for vmware-vmx.exe or
powercfg /powerthrottling disable /path "C:\Program Files (x86)\VMware\VMware Workstation\x64\vmware-vmx.exe"
(3) set affinity to only the p-cores via Task Manager or via vmx configuration

[Dryne]

Okay.  Other than this blues creen that I saw for the first time today, I face no performance issues at all.  My VMs are all speedy.

If I see this blue screen again, I will consider taking action.  For now I will ignore it.  I also left Windows 11 Pro with default settings.  I did not disable hypervisor as I used to do under Windows 10 for my VMs.  They are so fast that I will leave things as they are.

[Dryne]

I just experienced this same blue screen starting Windows 11 Pro guest today.  I was not facing this before, so I downloaded VMware-workstation-full-17.5.0-22583795.exe to install over the 17.5.1 update to see if this issue goes away.

 

[Dryne]

I uninstalled VMWare Workstation 17.5.1, reboot, then installed version 17.5.0.  My Windows 11 guest started without incident or issue as expected.  I will stop all VMWare updates until I am convinced the team knows what they are doing.  It seems they fixed issues others were having, and broke my perfectly working VMs.