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docs(idols-ai): record overnight mixed-memory voltage tests

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# Mixed memory on idols-ai
128G from JUHOR 2×48G + GLOWY 2×16G. Four DIMMs are required because 96G is insufficient.
128G from JUHOR 2×48G + GLOWY 2×16G. All four DIMMs are needed because 96G is insufficient.
## Target configuration
This is the best configuration tested so far and the target for normal use. It passed a **6-hour
100G stress test with 0 errors**; highest sampled memory temperature: **56.8°C**. Keep these
settings rather than increasing voltage further.
| Field | Target |
| ----------------------- | ------------------------- |
| XMP | Disabled |
| Gear mode | Gear2 |
| Memory speed | 4800 MT/s |
| CPU VDD2 | **1.17 V fixed** |
| VCCSA | Auto (BIOS reads 1.288 V) |
| DRAM VDD | **1.28 V fixed** |
| DRAM VDDQ | **1.28 V fixed** |
| DRAM VPP | Auto (1.8 V) |
| tCL / tRCD / tRP / tRAS | 40 / 40 / 40 / 77 |
Displays stayed on during the passing test. Daily-use stability and display-off transitions still
need checking. Both voltage and the screen condition changed from the failed run, so their
individual effects have not been isolated.
## Hardware
- CPU: Intel Core Ultra 7 270K Plus (Arrow Lake-S Refresh, LGA1851).
- Board: Colorful CVN Z890 ARK FROZEN V20, BIOS version 1013; four DDR5 slots, rated up to 192G.
- Layout: each channel has 48G (2R) in DIMM0 and 16G (1R) in DIMM1.
- The 16G pair was added on 2026-10-06. XMP is off; both kits run at 4800 MT/s.
- CPU: Intel Core Ultra 7 270K Plus.
- Board: Colorful CVN Z890 ARK FROZEN V20, BIOS 1013.
- Each channel: 48G (2R) in DIMM0, 16G (1R) in DIMM1.
- The 16G pair was added on 2026-10-06.
| Kit | Capacity | XMP rating | Timings | Voltage | Rank | Part number |
| ----- | -------- | ---------- | ------------- | ------- | ---- | --------------------- |
@@ -16,94 +38,41 @@
## Bring-up and recovery
The working bring-up order starts with the 16G pair. Earlier attempts starting with the 48G pair or
all four DIMMs did not reach BIOS.
Earlier attempts starting with the 48G pair or all four DIMMs did not reach BIOS. Working order:
1. Install only the 2×16G in `ChannelA-DIMM1` / `ChannelB-DIMM1`.
2. Enter BIOS; set `内存模块资源 = 默认模块` (XMP off). DRAM voltage returned to 1.25 V.
2. Enter BIOS and disable XMP.
3. Power off and add the 2×48G in DIMM0.
4. Allow retraining (1–3 minutes, possibly several reboots).
5. Set Gear2 and DRAM VDD/VDDQ to 1.280 V. The latest CPU VDD2 experiment uses 1.150 V.
4. Allow 1 to 3 minutes for retraining, possibly with several reboots.
5. Apply the target settings above.
If failed training prevents BIOS entry, repeat this order. If necessary, clear CMOS first.
If failed training prevents BIOS entry, repeat this order; clear CMOS first if necessary. Failed
training can silently restore defaults; re-check settings in BIOS afterwards.
## Current BIOS settings
## Test results
`超频OC → 内存设置`, as of 2026-10-09. CPU VDD2 1.150 V passed BIOS checks and the 100G short test;
stability in daily use remains to be checked.
Earlier DRAM tests used CPU VDD2 Auto (BIOS reading 1.104 V). **Bold values identify the rails
changed in each test.**
| Field | Setting / BIOS reading |
| ------------------------------- | ------------------------------------ |
| `内存模块资源` | `默认模块` (XMP off) |
| `Gear选择` | Gear2 |
| `内存频率(MHz)` | 4800 |
| `CPU VDD2电压` | **1.150 V fixed** / 1.152 V |
| `VCCSA电压` | Auto / 1.288 V |
| `Vdd2Mv` | Auto / 1.280 V; meaning not verified |
| `Memory Voltage VDD` | 1.280 V fixed |
| `内存电压VDDQ` | 1.280 V fixed |
| `内存电压VPP` | Auto / 1.800 V |
| `tCL` / `tRCD` / `tRP` / `tRAS` | 40 / 40 / 40 / 77 |
| CPU VDD2 | DRAM VDD | DRAM VDDQ | Result | Highest sampled memory temperature |
| ---------- | ------------------------ | ------------------------ | ------------------------------------------------------------ | ---------------------------------- |
| Auto | **1.10 V** | **1.10 V** | Immediate freezes during memory tests, even 4G. | Not recorded |
| Auto | **1.25 V** | **1.25 V** | 8G / 32G / 100G short tests passed; llama.cpp load froze. | Not recorded |
| Auto | **1.28 V** | **1.28 V** | 100G short test passed; daily use froze twice on 2026-10-08. | Not recorded |
| Auto | **1.282 V** | **1.282 V** | Display corruption in BIOS. | Not recorded |
| Auto | **1.29 / 1.30 / 1.32 V** | **1.29 / 1.30 / 1.32 V** | Each setting failed training. | Not recorded |
| **1.13 V** | 1.28 V | 1.28 V | BIOS normal; no long test. | Not recorded |
| **1.15 V** | 1.28 V | 1.28 V | 100G, 15 minutes: PASS. | 45.5°C* |
| **1.15 V** | 1.28 V | 1.28 V | Long test froze; last saved duration: 21 minutes 17 seconds. | 56.5°C |
| **1.17 V** | 1.28 V | 1.28 V | 100G, **6 hours: PASS**, displays kept on. | **56.8°C** |
| **1.20 V** | 1.28 V | 1.28 V | BIOS display corruption and freeze within 10 to 20 seconds. | Not recorded |
`dmidecode` reports firmware-configured DIMM speed/voltage, not measured CPU VDD2 or VCCSA. Re-check
BIOS settings after failed training: the board can silently restore defaults.
*The 15-minute test used sparse temperature samples; its true peak is unknown. Long tests sampled
about every 5 seconds and used a 60°C stop threshold.
## Voltage tests
Both recent long tests were on 2026-10-09:
Earlier DRAM tests used CPU VDD2 Auto (baseline BIOS reading 1.104 V). CPU VDD2 tests keep both DRAM
rails at 1.280 V. **Bold values are the parameters varied in each test.**
| CPU VDD2 | DRAM VDD | DRAM VDDQ | Result | Highest sampled DIMM temperature |
| ---------- | ------------------------ | ------------------------ | ----------------------------------------------------------------------------------------- | -------------------------------- |
| Auto | **1.10 V** | **1.10 V** | Immediate memory-test freezes, even 4G. | — |
| Auto | **1.25 V** | **1.25 V** | 8G / 32G / 100G short tests passed; real llama.cpp load hard-froze. | — |
| Auto | **1.28 V** | **1.28 V** | 100G short test passed; daily use still froze around 16:40 and after 23:00 on 2026-10-08. | — |
| Auto | **1.282 V** | **1.282 V** | Reached BIOS, then display corruption. | — |
| Auto | **1.29 / 1.30 / 1.32 V** | **1.29 / 1.30 / 1.32 V** | Each setting failed training. | — |
| **1.13 V** | 1.28 V | 1.28 V | BIOS operation normal; no long-term test. | — |
| **1.15 V** | 1.28 V | 1.28 V | 2026-10-09: 100G / 900.34 s PASS, exit 0, 0 hardware incidents, 0 errors. | 45.5°C* |
| **1.20 V** | 1.28 V | 1.28 V | BIOS display corruption and freeze within about 10–20 s; failed setting. | — |
*45.5°C is the highest of sparse samples during the run; the true peak is unknown. No temperature
record is available for the other tests. Future tests should sample periodically throughout the run.
DRAM 1.28 V is the best setting tried, but is confirmed unstable with CPU VDD2 Auto. The current
experiment changes only CPU VDD2 to 1.15 V to address those freezes. Keep VCCSA, Gear, frequency,
and DRAM rails unchanged. Do not repeat the failed 1.20 V CPU VDD2 setting.
Frequency changes and DIMM-removal experiments are excluded: this BIOS requires a profile that
rewrites many settings to change frequency, and the full 128G capacity is required.
## Stress testing
Save logs in persistent `~/tmp`; files directly under `~/` are ephemeral. Example 100G / 15-minute
run:
```bash
SP=$(nix build --no-link --print-out-paths nixpkgs#stressapptest)
set -o pipefail
stdbuf -oL -eL "$SP/bin/stressapptest" -s 900 -M 100000 -v 4 2>&1 | tee ~/tmp/memtest-100G.log
```
Pass requires exit 0, `Found 0 hardware incidents`, and `Status: PASS`. A short pass does not
establish stability in real workloads; earlier passing settings still hard-froze.
## Firmware-change checklist
BIOS changes can break LUKS TPM auto-unlock (PCR 0+7). After settings are final, re-enroll both
disks by partlabel; preserve the passphrase slot:
```bash
for d in /dev/disk/by-partlabel/disk-nixos-ai-root /dev/disk/by-partlabel/disk-data-datapart; do
sudo systemd-cryptenroll --wipe-slot=tpm2 "$d"
sudo systemd-cryptenroll --tpm2-device=auto --tpm2-pcrs=0+7 "$d"
done
```
Secure Boot check: `sudo sbctl status`.
## Open items
- [ ] Check overnight and daily-use stability with CPU VDD2 1.150 V and DRAM VDD/VDDQ 1.280 V.
- [ ] After hard freezes, check for store/filesystem corruption:
`nix-store --verify --check-contents --repair` and `btrfs scrub`.
- At 1.15 V, the last record was at 01:02, with machine uptime of 1 hour 53 seconds. The saved
durations are lower bounds, not exact freeze times.
- At 1.17 V, the test ran from 01:29 to 07:30, with 0 errors or hardware incidents and no swap use.
Recorded temperatures stayed below 60°C.