PC

Core Ultra 9 285K + ROG Maximus Z890 Hero: DDR5-7800 kit fails TestMem5 (XMP I / II / Tweaked), 7600 profile won’t POST, 5600 is rock solid. What am I missing?

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Core Ultra 9 285K + ROG Maximus Z890 Hero: DDR5-7800 kit fails TestMem5 (XMP I / II / Tweaked), 7600 profile won't POST, 5600 is rock solid. What am I missing?

Hi everyone, I'm stuck on getting my kit to run at its rated speed and would love advice from anyone with a similar setup.

My system

  1. – CPU: Intel Core Ultra 9 285K
  2. – Board: ASUS ROG Maximus Z890 Hero, BIOS 3401
  3. – RAM: Patriot Viper Xtreme 5 RGB, 32 GB (2×16), DDR5-7800 CL38 (PVXR532G78C38K), 1.45 V. The kit stores three XMP profiles: 7800 38-48-48-84, 7600 36-48-48-84 and 7400 36-44-44-110, all at 1.45 V.
  4. – Slots: A2/B2 (I first had them in A1/B1 by mistake and moved them)
  5. – Cooling: ROG Ryujin III 360 AIO. Storage: Crucial T705 1 TB. PSU: ROG Thor 1200 W. OS: Windows 11 Pro.

Everything else is at default. No manual voltages so far, MCE and SVID left on Auto.

What happened:

After building the PC I enabled XMP II and it ran at 7800 in Windows without problems. Then I got one crash (the Windows 11 black crash screen, stop code MEMORY_MANAGEMENT, 0x1A; the crash log also showed a 0x1E with 0xC000001D) right after I woke the PC and was playing with fan control in Armoury Crate. It then hung at 0% while writing the dump.. I uninstalled Armoury Crate afterwards, and I still get memory errors in testing, so I don't think it's the cause.

TestMem5 results (0.13.1, anta777 configs, 24 threads, about 20 GB tested)

XMP II, 7800: Extreme @ anta777 errored in test 4.

XMP I, 7800: Extreme ran about 19 minutes, then errored in test 6. The DDR5 Intel @ anta777 config errored at 6:43.

XMP Tweaked (the ASUS option that adds DRAM refresh interval 32768, NGU 32, D2D 32), 7800: Extreme passed 1:37:39 with 0 errors. Memory temps were about 66 C under load, CPU up to about 71 C, VDD/VDDQ about 1.455 V, and PMIC flags were all fine. Then Intel config on the same profile errored at 46:41 in test 10.

Next morning, after a cold boot, Tweaked 7800 failed within seconds. DDR5 Intel errored at 9 s (test 2) and at 13 s (test 6) after a restart, and Extreme errored at 18 s (test 4).

XMP Tweaked + the 7600 profile (CL36): training failed several times, the board shut down and retried, and I ended up in safe mode at DDR5-4000 ("system has POSTed in safe mode").

Ai Overclock Tuner = Auto (DDR5-5600): DDR5 Intel @ anta777 passed 1:31:11, 28 cycles, 0 errors.

So the sticks, the slots and the board look healthy, and the problem seems to be the memory controller at 7600 and above. Even the same config that passed for 90 minutes one day failed in seconds the next day, so memory training seems to differ from boot to boot.

Extra details

In the BIOS monitor, the board sets MC (memory controller) voltage to about 1.42 V on Auto at 7800, and 1.10 V at the fallback 4000 speed.

DRAM Frequency Ratio (gear) is on Auto, DIMM Flex is Disabled, and the rest of the memory settings are Auto.

HWiNFO shows DDR5-7800 38-48-48-84 at 1.45 V, D2D/NGU at 3200 MHz under the Tweaked profile.

What I'm asking

  1. Is 7800 on a 285K realistically stable, or is it mostly a silicon lottery on the IMC? What's your experience with 7600+?
  2. Which settings made it stable for you (VDD2/MC voltage, SA voltage, VDDQ, gear mode, Memory Context Restore, training options)?
  3. Is the boot-to-boot variation (passes one day, fails in seconds the next) a known thing on Z890/Arrow Lake?
  4. Any known issues with this Patriot 7800 kit on Z890 boards, or should I just settle somewhere like 6400-7200 and test each step?
  5. Any better test than TestMem5 you'd recommend (I plan to run MemTest86 overnight when I can)?

I'm happy to post more screenshots of the BIOS pages or HWiNFO or of anything if useful. I'm being careful and don't want to blindly raise voltages, so I'd appreciate explanations along with any numbers.

Thanks a lot!