MSI B550 Tomahawk MAX WiFi - Random Reboots While Gaming (CS2 & THE FINALS) - WHEA Logger Event 18 (Cache Hierarchy Error)

[oxtrade615a502e6]

Hi everyone,
I'm looking for help before proceeding with an RMA.

System Specifications​

• Motherboard: MSI MAG B550 Tomahawk MAX WiFi (8 months old)
• CPU: AMD Ryzen 5 5600X
• GPU: AMD Radeon RX 6650 XT
• RAM: 32GB (2×16GB) Corsair Vengeance LPX DDR4-3200 CL18
• PSU: Corsair RM850x Shift 850W (80+ Gold)
• UPS: Artis 2000VA Line Interactive UPS with AVR
• CPU Cooler: Dual-tower air cooler (cleaned and repasted recently)
• BIOS: Latest version

Problem​

For the past one month, my PC has been randomly rebooting only while gaming.

Affected games:

Counter-Strike 2​

THE FINALS​

​

The reboot usually happens:

• During game launch
• During the intro/loading screen
• While joining a match
• Occasionally a few minutes into gameplay

There is no BSOD. The PC instantly reboots.

Event Viewer​

Every reboot logs the following error:

WHEA Logger - Event ID 18
Reported by component: Processor Core
Error Source: Machine Check Exception
Error Type: Cache Hierarchy Error
The Processor APIC ID changes between crashes. I've seen IDs:
0, 4, 6, 7, 10 and 11.

Stress Tests Completed​

All of these pass successfully without any reboot:

• OCCT CPU Test
• OCCT Power Test (30 minutes)
• Cinebench Multi-Core
• Cinebench Single-Core
• Heaven Benchmark

CPU and GPU temperatures remain completely normal during these tests.

Hardware Troubleshooting Already Performed​

• Updated to the latest BIOS
• Loaded BIOS defaults
• Disabled PBO
• Tested XMP and default memory settings
• Removed CPU cooler
• Cleaned CPU and applied fresh thermal paste
• Reseated CPU
• Reseated RAM
• Reseated GPU
• Cleaned all dust from the system

The problem still persists.

Monitoring​

I recorded multiple HWiNFO logs before crashes.
Everything looks normal before the reboot:

• CPU temperatures normal
• GPU temperatures normal
• VRM temperatures normal
• Chipset temperatures normal
• 12V rail stable
• No visible overheating or voltage drop

The log simply stops, then Windows records WHEA Event ID 18 after reboot.

Power Troubleshooting​

To rule out power issues, I tested:

• Different wall sockets
• Mains power
• Home inverter
• Artis 2000VA UPS with AVR

The issue still occurs.

My Questions​

Has anyone experienced similar random reboots with the MSI MAG B550 Tomahawk MAX WiFi?
Since every stress test passes but games trigger WHEA Logger Event ID 18 (Cache Hierarchy Error), could this indicate:

• A faulty motherboard?
• CPU power delivery issue?
• Faulty CPU?
• Something specific to this motherboard or BIOS?

Thank you!

 

[ericj159802e9]

This topic at HWInfo forums might hold some clues: https://www.hwinfo.com/forum/thread...dden-reboots-on-amd-ryzen-systems.7041/page-8 .

 

[oxtrade615a502e6]

Thanks for the suggestion.
I tested with HWiNFO completely closed after a fresh reboot (no HWiNFO logging or monitoring running). Unfortunately, the PC still rebooted while launching THE FINALS, and Event Viewer again logged:

• WHEA Logger Event ID 18
• Machine Check Exception
• Cache Hierarchy Error

So it doesn't appear that HWiNFO itself is triggering the issue on my system. I also tested with BIOS defaults (XMP disabled, RAM running at JEDEC 2666 MHz), and the problem still persists.

Thanks again for pointing me to the thread—it was worth checking.

 

[ericj159802e9]

At the Steam forums there is an 11 page topic about this error: https://steamcommunity.com/discussions/forum/11/6367585249991479633/?l=hungarian .

To rule out power issues, I tested:

• Different wall sockets
• Mains power
• Home inverter
• Artis 2000VA UPS with AVR

My attention got piqued by this. Could you explain in a bit more detail how you tested for power issues? A general question. Does the stability of electrical power in your country require a UPS? What do you mean with home inverter and how did you test with it?

 

[oxtrade615a502e6]

Thank you for your question.
To rule out power-related issues, I tested the PC in the following configurations:

• Connected directly to different wall outlets (bypassing the UPS).
• Connected through my Artis 2000VA Line Interactive UPS with AVR.
• Connected through my home inverter backup system during a power outage.

In all three scenarios, the behavior was the same. The PC still randomly rebooted only while launching or playing Counter-Strike 2 and THE FINALS.

During the reboots, the UPS did not beep, did not report an overload, and did not switch unexpectedly to battery mode. Because the issue occurs regardless of the power source used, I currently suspect the problem is inside the PC rather than the AC power supplied to it.

I also reviewed the Steam discussion you shared. I have already performed many of the troubleshooting steps mentioned there, including updating the BIOS, installing the latest AMD chipset driver, performing a clean GPU driver installation using DDU, clearing CMOS, disabling PSS Support and Global C-State Control, testing with another PSU, and running multiple stress tests (OCCT CPU/Power, Cinebench, and Heaven), all of which passed successfully. Unfortunately, none of these steps resolved the issue.

 

[Alan J T]

Reading your testing, I would say the cause is that the CPU is not stable