docs(hosts): refresh the ai screenshots and correct its hardware notes

- replace the btop screenshot with the 2026-10-06 annotated capture
  (btop + fastfetch + the strata/llama.cpp serving logs); the old
  2026-10-01 file is gone, so the README link moves to the new name
- drop the Helix/AI-agents screenshot and its README reference
- fix stale hardware descriptions: the hosts/README.md inventory row and
  the idols-ai header comment still said i5-13600KF, and the zswap pool
  comment sized its percentages against the old 96G of RAM (now 128G)
- record the hardware history: the platform was rebuilt on 2026-04-27
  (PR #257/#258) onto the Colorful CVN Z890 ARK FROZEN + Core Ultra 7
  270K Plus, replacing the MSI board and i5-13600KF the host was added
  with in 2023-05; the 2x48G kit predates that rebuild, the 2x16G kit
  was added 2026-10-06
- make the DIMM bring-up order mandatory and record its failure mode:
  with the 48G pair in first, or all four DIMMs from the start, the
  board does not POST
- gloss the Chinese BIOS labels in English, marked as translations of
  the labels rather than the firmware's own English wording

Left alone on purpose: the 96G swapfile in hosts/idols-ai/disko-fs.nix.
It was grown from 20G to 1x-RAM on 2026-10-02 (a26ab3be), when the host
still had 96G; resizing it again means re-running disko on the machine,
so that stays a separate decision.

README.md

@@ -82,9 +82,7 @@ Wallpapers: https://github.com/ryan4yin/wallpapers
 
 ![desktop](./_img/2026-10-02_niri-noctalia_desktop.webp)
 
-![btop monitoring and system information](./_img/2026-10-01_btop-monitoring-system-info.webp)
-
-![Helix and AI agents in a terminal workspace](./_img/2026-10-02_helix-ai-agents.webp)
+![btop, fastfetch, and llama.cpp serving logs](./_img/2026-10-06_btop-monitoring-system-info.webp)
 
 ## Editors / IDE
 

hosts/README.md

@@ -10,17 +10,30 @@ This directory contains all host-specific configurations for my NixOS and macOS
 
 Named after characters from "Oshi no Ko":
 
-| Host         | Platform        | Hardware              | Purpose               | Status      |
-| ------------ | --------------- | --------------------- | --------------------- | ----------- |
-| `ai`         | NixOS           | i5-13600KF + RTX 4090 | Gaming & Daily Use    | ✅ Active   |
-| `aquamarine` | NixOS (libvirt) | Virtual               | Monitoring & Services | ⚪ Not Used |
-| `kana`       | NixOS (libvirt) | Virtual               | Run AI Agents         | ✅ Active   |
-| `ruby`       | NixOS (libvirt) | Virtual               | Run AI Agents         | ✅ Active   |
-| `akane`      | NixOS (aarch64) | Virtual (UTM)         | aarch64 test VM       | ✅ Active   |
+| Host         | Platform        | Hardware                                | Purpose               | Status      |
+| ------------ | --------------- | --------------------------------------- | --------------------- | ----------- |
+| `ai`         | NixOS           | Ultra 7 270K Plus + RTX 4090, 128G DDR5 | Gaming & Daily Use    | ✅ Active   |
+| `aquamarine` | NixOS (libvirt) | Virtual                                 | Monitoring & Services | ⚪ Not Used |
+| `kana`       | NixOS (libvirt) | Virtual                                 | Run AI Agents         | ✅ Active   |
+| `ruby`       | NixOS (libvirt) | Virtual                                 | Run AI Agents         | ✅ Active   |
+| `akane`      | NixOS (aarch64) | Virtual (UTM)                           | aarch64 test VM       | ✅ Active   |
 
 `aquamarine` is retired; its services now run directly on `youko`
 (`hosts/12kingdoms-youko/homelab-services/`).
 
+On 2026-04-27 `ai` was rebuilt on a new platform. The MSI board and i5-13600KF it was added with in
+2023-05 (the host was originally named `msi-rtx4090`) gave way to the Colorful CVN Z890 ARK FROZEN +
+Intel Core Ultra 7 270K Plus. The traces in the history are PR #257 (the NIC moved from `enp5s0` to
+`enp130s0`) and PR #258 (Niri output names renamed, `hardware-intel.nix` added with the Arrow Lake
+NPU, kernel moved to `linuxPackages_latest`). The 2×48G DDR5 kit was already in place at that point;
+the repo has no record of when it went in.
+
+On 2026-10-06 `ai` grew from 2×48G (96G) to 2×48G + 2×16G (128G) across all four DIMM slots, at
+DDR5-4800 with XMP off — the only stable setting with four DIMMs on this board. The 16G pair must be
+installed first; with the 48G pair in first the board does not POST. The bring-up order, the BIOS
+settings, the stress-test recipe, and how to recover a board that will not POST are in
+[`idols-ai/MIXED-MEMORY.md`](./idols-ai/MIXED-MEMORY.md).
+
 #### `darwin` - macOS Systems
 
 Named after characters from "Frieren: Beyond Journey's End":

hosts/idols-ai/MIXED-MEMORY.md

@@ -22,18 +22,22 @@ Notes from adding a 2×16G kit to the existing 2×48G kit on this desktop.
 | JUHOR | 2×48G    | DDR5-5600 (PC5-44800) | CL46-45-45-90 | 1.25 V  | 2R   | `JHE5600U4648JG`      |
 | GLOWY | 2×16G    | DDR5-6400 (PC5-51200) | CL32-38-38-90 | 1.35 V  | 1R   | `VGM5UH64C32AG-DTACW` |
 
+- When they went in: the 2×16G GLOWY kit was added 2026-10-06; the 2×48G JUHOR kit was already in
+  place when the platform was rebuilt 2026-04-27 (before that the host was an MSI LGA1700 board with
+  an i5-13600KF — see the `hosts/README.md` inventory notes).
 - Channel A/B, DIMM0 = 48G (2R), DIMM1 = 16G (1R) → 64G per channel, 128G total.
 - With XMP off both kits run at JEDEC DDR5-4800; the board exposes one XMP profile per kit
-  (`XMP 模块一` / `XMP 模块二`).
+  (`XMP 模块一` / `XMP 模块二`, XMP profile 1 / profile 2).
 
 ## Bring-up order (install the 16G pair first)
 
-The install order matters — starting from all four DIMMs often fails to train:
+The order is mandatory. Starting from the 2×48G, or from all four DIMMs, does not POST: no BIOS
+entry and nothing to change in setup — pull the 48G pair and start from step 1.
 
 1. Insert **only the 2×16G**, in the board's primary slots (the first-populate pair the manual
    marks; the working layout has them in `ChannelA-DIMM1` / `ChannelB-DIMM1`).
-2. Boot to BIOS; confirm `内存模块资源 = 默认模块` (XMP off) — the DRAM voltage comes back at 1.25
-   V.
+2. Boot to BIOS; confirm `内存模块资源 = 默认模块` (memory module source = default module, i.e. XMP
+   off) — the DRAM voltage comes back at 1.25 V.
 3. Power off, then insert the **2×48G** in the remaining slots.
 4. Boot; the board retrains once (1–3 min, possibly a few reboots), then works.
 
@@ -43,21 +47,23 @@ Resulting layout: `ChannelA/B-DIMM0` = 48G (2R), `ChannelA/B-DIMM1` = 16G (1R).
 
 - Verified: `stressapptest` 8G / 32G / 100G all PASS, 0 hardware incidents.
 
-Current BIOS settings (`超频OC → 内存设置`):
+Current BIOS settings (`超频OC → 内存设置`, the Overclocking → Memory settings page). The BIOS was
+used in Chinese; the English in the table translates those labels and is not the firmware's own
+English wording:
 
-| Field                                   | Value                 |
-| --------------------------------------- | --------------------- |
-| `内存模块资源` (module source)          | `默认模块` (XMP off)  |
-| `Gear选择` (gear)                       | `Gear2`               |
-| `内存频率(MHz)`                         | `4800`                |
-| `CPU VDD2电压`                          | `1.104 V` (Auto)      |
-| `VCCSA电压`                             | `1.288 V` (Auto)      |
-| `Vdd2Mv`                                | `1.250 V` (Auto)      |
-| `Memory Voltage VDD`                    | **`1.250 V`** (fixed) |
-| `内存电压VDDQ`                          | **`1.250 V`** (fixed) |
-| `内存电压VPP`                           | `1.800 V` (Auto)      |
-| `Primary Timing` `tCL` / `tRCD` / `tRP` | `40` / `40`           |
-| `Primary Timing` `tRAS`                 | `77`                  |
+| Field                                   | Value                                |
+| --------------------------------------- | ------------------------------------ |
+| `内存模块资源` (memory module source)   | `默认模块` (default module, XMP off) |
+| `Gear选择` (Gear mode)                  | `Gear2`                              |
+| `内存频率(MHz)` (DRAM frequency)        | `4800`                               |
+| `CPU VDD2电压` (CPU VDD2 voltage)       | `1.104 V` (Auto)                     |
+| `VCCSA电压` (VCCSA voltage)             | `1.288 V` (Auto)                     |
+| `Vdd2Mv`                                | `1.250 V` (Auto)                     |
+| `Memory Voltage VDD`                    | **`1.250 V`** (fixed)                |
+| `内存电压VDDQ` (DRAM VDDQ voltage)      | **`1.250 V`** (fixed)                |
+| `内存电压VPP` (DRAM VPP voltage)        | `1.800 V` (Auto)                     |
+| `Primary Timing` `tCL` / `tRCD` / `tRP` | `40` / `40`                          |
+| `Primary Timing` `tRAS`                 | `77`                                 |
 
 The only hand-set voltages are the two DRAM rails, `Memory Voltage VDD` and `内存电压VDDQ`, both
 **1.250 V** (the fields read `1.250`, not `Auto`) — this is what `dmidecode` reports as

hosts/idols-ai/default.nix

@@ -7,7 +7,8 @@
 }:
 #############################################################
 #
-#  Ai - my main computer, with NixOS + I5-13600KF + RTX 4090 GPU, for gaming & daily use.
+#  Ai - my main computer, with NixOS + Core Ultra 7 270K Plus + RTX 4090 GPU,
+#  128G DDR5-4800 (mixed 4-DIMM, see MIXED-MEMORY.md), for gaming & daily use.
 #
 #############################################################
 let
@@ -50,7 +51,8 @@ in
   # - zstd: CPU is not the bottleneck here (llama.cpp peaks ~30% util); its ~2.5x ratio
   #   keeps ~5G more anon bytes in the capped pool than lz4, and ~5us decompress is noise
   #   vs the ~100us SSD fault it avoids.
-  # - 10% pool (~9G): the module default 25% (~23G) would compete with the weight cache.
+  # - 10% pool (~13G on 128G): the module default 25% (~32G) would compete with the weight
+  #   cache.
   boot.zswap = {
     enable = true;
     compressor = "zstd";