929-Fatal MCA Error detected CPU 0

[HK20]

We have a Z420 that will not boot. 

It returns:

929-Fatal MCA error.

CB0/LLC0 error detected CPU 0

Memory hierachy error

The Manual has no suggested fix.  Any Ideas?

Thanks!

[Dan_WGBU]

This could either be a memory failure (try reseating it, moving it to a different slot, or removing or replacing the memory), or a possible CPU failure.  (The system is reporting a CPU machine check error, but it could be caused by memory issues). 

Go into Computer Management, then click on Event Viewer, Windows Logs, and System.  Are there any WHEA warnings listed under Source?  An easier way to find them is to Filter Current Log, and select Critical, Warning, Verbose, and Error to filter out the (many) Information entries.

If the memory is OK, reseating the CPU might help, but this can be tricky.  The CPU socket pins are very easily bent during the removal or install process, and extrememly difficult or impossible to repair if damaged.  Also, when the CPU heatsink is removed, clean off the thermal paste on both the CPU and heatsink, and use new paste.  The paste hardens, and does not give good thermal conductivity if the heatsinks is removed and the paste is not replaced.  The CPU operating temperature can increase by 10 deg. C or more.  FYI.

If the system is under warranty, contact HP so they can fix it. 

[HK20]

Thank you the reply Dan_WGBU ,

I did try reseating and replacing the memory but as the PC is under warranty I did not touch the CPU. 

I will begin the warranty repair request.

[redefy]

Hello,

Did you ever get this resolved? what was the resolution?

We have this same issue.

[ready2assist]

We have seen replacing system board has fixed the issue.

In rare cases processor.