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`leno0` BIOS fan change #4

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Enter BIOS on the M715q #

  1. Shut down (or reboot) leno0.
  2. Plug in a USB keyboard (some USB ports wake late).
  3. Power on and tap F1 repeatedly until the blue Lenovo Setup Utility appears.
    • If you miss it: reboot and try again, or hold F1 from the first beep/LED.
  4. On newer setups you can also use Startup Interrupt if your model shows a boot menu (less common on M715q).

To save and exit: F10 → Yes, or Exit → Save changes and reset.

Fix 1 — Disable CSM (most important for “max fan at idle”) #

This is the fix that helped other M715q owners when temps were normal but the fan stayed loud.

  1. In BIOS, open the Startup tab (name may be Boot on some builds).
  2. Find CSM (Compatibility Support Module) or Legacy support.
  3. Set CSM to Disabled.
  4. Confirm boot mode is UEFI only (not Legacy / Legacy first).
  5. F10 → save and reboot.

Why: With CSM/Legacy on, firmware can ignore “quiet” fan settings even when NixOS boots in UEFI. Your NixOS install already uses systemd-boot (UEFI), so disabling CSM should not break boot.

If it won’t boot after: Re-enter BIOS (F1), re-enable CSM once, fix Startup boot order so the EFI entry / M.2 drive is first, disable CSM again, save.

Fix 2 — Set fan to quiet mode #

On ThinkCentre minis (M710q/M715q family), fan policy is usually under Power, not a separate “Fan” menu.

  1. Go to Power.
  2. Open Intelligent Cooling Engine (or Thermal / Cooling — wording varies).
  3. Set performance / thermal mode to Better acoustics (not Performance, Full speed, or similar).
  4. Leave Thermal alert enabled unless Lenovo docs say otherwise.
  5. F10 → save and reboot.

Listen at idle for a few minutes; EC fan curves can ramp down slowly after boot.

Fix 3 — Update BIOS (if settings look right but fan is still loud) #

  1. On another machine, open Lenovo support for ThinkCentre M715q.
  2. Download the latest BIOS Update for your exact sub-model (1st vs 2nd gen if listed).
  3. Copy the package to a USB stick or run Lenovo’s update from a supported environment per their readme.
  4. Flash, reboot, re-check CSM Disabled and Better acoustics (updates sometimes reset options).

Lenovo documents fan cycling between full and normal speed after S3 (sleep) on the M715q.

  • After suspend/resume: do a full reboot and see if fan returns to normal.
  • If you don’t need sleep on a server: in NixOS you can avoid suspend; in BIOS check Power for anything like ACPI sleep / S3 if you want to reduce use of sleep.

Optional checks (same BIOS session) #

Tab / area Suggestion
Startup → boot order M.2 / EFI NixOS entry first; no need for Legacy USB unless you use it
Advanced → CPU (AMD) If you tried “max performance” tweaks, Core Performance Boost can add heat; at 29°C this is usually not the main issue
Security Unrelated to fan; don’t change unless you know why

What “success” looks like #

  • Idle CPU still ~29–40°C (your k10temp readings).
  • Fan clearly quieter within a few minutes of boot.
  • Linux still has no fan*_input / hwmon pwm* — that’s expected; you’re fixing firmware policy, not installing a Linux fan daemon.

If it’s still loud after BIOS changes #

  • Reseat power, blow dust out of the tiny chassis (blocked vent → EC runs fan hard).
  • Confirm acoustics mode stayed saved (re-open F1 and check).
  • Physical fan bearing failure can sound loud without high CPU temp.

Order to try: CSM off → Better acoustics → BIOS update → reboot after any sleep test.

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