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XMP worked but getting MemTest warning on row hammer bitflips

Kaelon
Level 7
After some unrated/unqualified RAM was not being stable upon XMP-OC for my ASUS Maximus VIII Hero, I installed QVL-certified RAM -- 4x16 Gb G.Skill TridentZ DDR4-3400's, and the XMP-OC proved stable enough to survive 6+ hours of MemTest86 passes error-free.

However, on Test 13, I received a basic "Warning" on the screen, claiming that "RAM may be vulnerable to high frequency row hammer bit flips." Upon further evaluation at the MemTest Troubleshooting page, I discovered this language:

Memtest86 wrote:
Starting from MemTest86 v6.2, the user may see a warning indicating that the RAM may be vulnerable to high frequency row hammer bit flips. This warning appears when errors are detected during the first pass (maximum hammer rate) but no errors are detected during the second pass (lower hammer rate). See MemTest86 Test Algorithms for a description of the two passes that are performed during the Hammer Test (Test 13). When performing the second pass, address pairs are hammered only at the rate deemed as the maximum allowable by memory vendors (200K accesses per 64ms). Once this rate is exceeded, the integrity of memory contents may no longer be guaranteed. If errors are detected in both passes, errors are reported as normal.

The errors detected during Test 13, albeit exposed only in extreme memory access cases, are most certainly real errors. During typical home PC usage (eg. web browsing, word processing, etc.), it is less likely that the memory usage pattern will fall into the extreme case that make it vulnerable to disturbance errors. It may be of greater concern if you were running highly sensitive equipment such as medical equipment, aircraft control systems, or bank database servers. It is impossible to predict with any accuracy if these errors will occur in real life applications. One would need to do a major scientific study of 1000 of computers and their usage patterns, then do a forensic analysis of each application to study how it makes use of the RAM while it executes. To date, we have only seen 1-bit errors as a result of running the Hammer Test.

There are several actions that can be taken when you discover that your RAM modules are vulnerable to disturbance errors:

- Do nothing
- Replace the RAM modules
- Use RAM modules with error-checking capabilities (eg. ECC)


Has anyone else seen this before? How seriously should we care about this warning?

Thanks for your thoughts!
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