Memtest86 - Mem Error - Data Expected and Actual bit interpretation

[klchen]

I have several DIMMs failed memtest86 and come with similar failing symptoms
1. Failed addresses are random.
2. Expected/Actual data always has one bit got flipped.

My question is: I knew it could be memory fail, but can I say it is always fail the same DRAM component and same DQ? I am trying to conclude whether it is single DRAM issue or multiple DRAM issue. Single bit fail or multiple bit fail. not sure if I can get help from this forum. I appreciate in advance.

Test log A -> always lower 2nd Hex bit are different and always same bin bit flipped.
2025-09-10 15:32:46 - [MEM ERROR - Data] Test: 7, CPU: 15, Address: 13BB800C0, Expected: 00000800, Actual: 00000880
2025-09-10 15:33:13 - [MEM ERROR - Data] Test: 7, CPU: 8, Address: 1DC523E40, Expected: 00040000, Actual: 00040080
2025-09-10 15:33:13 - [MEM ERROR - Data] Test: 7, CPU: 5, Address: 1D03AC180, Expected: FFFEFFFF, Actual: FFFEFF7F
2025-09-10 15:33:15 - [MEM ERROR - Data] Test: 7, CPU: 14, Address: 1F6D2AEC0, Expected: 00000020, Actual: 000000A0
2025-09-10 15:33:15 - [MEM ERROR - Data] Test: 7, CPU: 15, Address: 1F857EF00, Expected: FEFFFFFF, Actual: FEFFFF7F

Test log B -> always lower 5th Hex bit is different and always same bin bit flipped.
2025-09-10 16:17:33 - [MEM ERROR - Data] Test: 4, CPU: 5, Address: 13D38DBC9C, Expected: 80808080, Actual: 80818080
2025-09-10 16:17:37 - [MEM ERROR - Data] Test: 4, CPU: 1, Address: 1442D25A9C, Expected: FEFEFEFE, Actual: FEFFFEFE
2025-09-10 16:17:42 - [MEM ERROR - Data] Test: 4, CPU: 12, Address: 14ED2F890C, Expected: 7F7F7F7F, Actual: 7F7E7F7F
2025-09-10 16:17:42 - [MEM ERROR - Data] Test: 4, CPU: 1, Address: 14C346D50C, Expected: EFEFEFEF, Actual: EFEEEFEF
2025-09-10 16:17:42 - [MEM ERROR - Data] Test: 4, CPU: 7, Address: 14DB88A5FC, Expected: EFEFEFEF, Actual: EFEEEFEF
2025-09-10 16:17:42 - [MEM ERROR - Data] Test: 4, CPU: 3, Address: 14C8B81E3C, Expected: EFEFEFEF, Actual: EFEEEFEF
2025-09-10 16:17:47 - [MEM ERROR - Data] Test: 4, CPU: 3, Address: 154888570C, Expected: 20202020, Actual: 20212020
2025-09-10 16:17:47 - [MEM ERROR - Data] Test: 4, CPU: 1, Address: 15430B90CC, Expected: F7F7F7F7, Actual: F7F6F7F7
2025-09-10 16:17:47 - [MEM ERROR - Data] Test: 4, CPU: 5, Address: 1552D5A9FC, Expected: 20202020, Actual: 20212020
2025-09-10 16:17:51 - [MEM ERROR - Data] Test: 4, CPU: 5, Address: 15D319D69C, Expected: DFDFDFDF, Actual: DFDEDFDF
2025-09-10 16:17:53 - [MEM ERROR - Data] Test: 4, CPU: 5, Address: 1610D0F62C, Expected: 08080808, Actual: 08090808
2025-09-10 16:18:00 - [MEM ERROR - Data] Test: 4, CPU: 10, Address: 16E4E0DB4C, Expected: 04040404, Actual: 04050404
2025-09-10 16:18:00 - [MEM ERROR - Data] Test: 4, CPU: 4, Address: 16CE74B72C, Expected: 08080808, Actual: 08090808
2025-09-10 16:18:07 - [MEM ERROR - Data] Test: 4, CPU: 7, Address: 17998DE26C, Expected: 40404040, Actual: 40414040
2025-09-10 16:18:11 - [MEM ERROR - Data] Test: 4, CPU: 1, Address: 18010F2AFC, Expected: 08080808, Actual: 08090808
2025-09-10 16:18:11 - [MEM ERROR - Data] Test: 4, CPU: 0, Address: 183EE3B62C, Expected: 08080808, Actual: 08090808
2025-09-10 16:18:12 - [MEM ERROR - Data] Test: 4, CPU: 6, Address: 1816721C2C, Expected: EFEFEFEF, Actual: EFEEEFEF
2025-09-10 16:18:12 - [MEM ERROR - Data] Test: 4, CPU: 2, Address: 1805D14D5C, Expected: F7F7F7F7, Actual: F7F6F7F7

[David (PassMark)]

Single bit flips are almost always bad RAM.

On some systems the Pro version of MemTest86 can decode the individual chip at fault.
https://www.memtest86.com/tech_DIMM_Decoding.html

[Roxxors]

If you know how to, go in and tweak your BIOS. I got from like 500 errors like that to zero with just a couple of changes to the BIOS... The trick is figuring out what setting you need to change...

[David (PassMark)]

Yes, sometimes RAM issues can be "fixed", or at least hidden, by lowering the clock speeds, increasing the latency and / or slightly increasing the voltage.
But for most people this is a waste of time. RAM warranties are very long.

The only time this makes sense to me is when it is a laptop with soldered RAM and the laptop is also out of warranty.

For reference here is a typical list of timing variables that can be played around with. It's complex. And playing around in BIOS is beyond most people. Best to use the built in JEDEC and XMP profiles the experts have come up with.