Help: 265kf new build with repeat memtest86 errors across multiple memory kits

[pdayday]

Hey everyone. This is my third build, but my first in 7 years or so. The build generally went well. The only problem I had (which I have now solved) is that I couldn't get the splash screen to show. I am getting repeated errors on test 7 of memtest86 with multiple kits of memory, but only when run dual channel (2 sticks). This is a new PC, and the only carryover parts are my GPU (for now) and drives. The plan was to get by with the old gpu until the 50-series super cards, but now that those are delayed or dead, I will likely be getting a 5070ti or 5080. At this point the wait for a GPU is just to see if I can find a black Friday or holiday deal.

Anyway, I have run 10+ memtest86 tests, and aside from one pre-bios-update test, I am only having failures only on test 7 and only in dual channel. I thought the problems were gone after the Bios update. I can't tell for sure but it seems like it's getting worse, regardless of which memory kit is installed. The fact that it only happens in dual channel, and the same issue reoccurs across multiple memory kits, seems like it's NOT the memory. Is it a motherboard or CPU issue? Do I RMA my Mobo next? Is this some sort of an issue with my Bios getting the two kits confused and not resetting, voltage/timings?

I can post pictures of the test results if it's helpful.

System

CPU: 265KF

Mobo: ASRock Z890 Riptide Wifi

Memory: (A) Patriot Viper Venom 64gb DDR5 6400mhz 32-40-40-84 1.4v, (B) G.Skill Trident Z5 Royal 96gb 6400mhz 32-39-39-102 1.35v

GPU: EVGA FTW3 1080ti

PSU: Corsair RM1000x

Drives: 990 Pro 2tb nvme, SX8200 1tb nvme, 850 evo 2tb sata, sp550 480gb sata, hynix gold s31 250gb sata, barracuda 2tb sata

Step-by-step

1. I built the system using memory (A), booted and got basic programs installed, and played a few rounds of arc raiders.
2. Ran TEST1 memtest86, 4 passes, and had 17 failures on pass 4 across multiple different tests.
3. Ordered memory (B) because prices were skyrocketing and it didn't want to wait for them to get worse while I troubleshot my issues
4. Updated Bios to latest version (3.0
5. Reset a few settings in Bios
   
   a. enabled xmp profile 1 (6400mhz, 32-40-40-84)
   
   b. adjusted some fan speeds
6. Ran TEST2 memtest86, 4 passes, no errors
7. Enabled 200s in Bios
8. Ran TEST3 memtest86, 4 passes, no errors
9. Used the PC for a few days and memory (B) arrived.
10. Installed memory (B). I figured that if the non-QVL memory was working with XMP profile 1, then the QVL listed memory would surely work, and I wanted to bump up to 96gb anyway. I did not change, reset or update any settings in Bios.
11. Opened Bios, and despite not changing anything, it appeared to show the right speed and timings for XMP Profile 1 for memory (B).
12. TEST4 memtest86, 1392 errors on pass 1, test 7. Stopped the test.
13. TEST5 memtest86, 4 passes. removed memory from slot 4 from CPU (SN ending 95 in slot 2). no errors.
14. TEST6 memtest86, 4 passes. swapped the second stick in to slot 2 (SN 96 in slot 2). no errors.
15. TEST7 memtest86, 4 passes. SN96 in slot 4. no errors.
16. Reset Bios, enabled XMP profile 1, enabled 200s.
17. TEST8 memtest86, 4 passes. back to SN95 in slot 2, SN96 in slot 4. 2743 errors in test 7 on 3 passes.
18. TEST9 (for completeness) memtest86, 4 passes, SN95 in slot 4. no errors.
19. Installed memory (A). Disabled XMP profile, booted, re-enabled XMP profile 1.
20. TEST10 memtest86, 4 passes, memory (A), unknown slot order. 3594 errors on test 7, spread across all 4 passes.
21. ??? What do I do next?

[David (PassMark)]

> Enabled 200s in Bios

What is 200s ?

Did you try running without XMP (or was Step 2 without XMP)?

For memory A) and B) is there two sticks in each kit? (2 x 32GB and 2 x 48GB)

Did you try using the other two slots on the motherboard (Slot 1 & 3). I assume this would still allow you to get into dual channel mode.