diff --git a/docs/plans/pn51-stability.md b/docs/plans/pn51-stability.md
index 427c9e3..132a4fb 100644
--- a/docs/plans/pn51-stability.md
+++ b/docs/plans/pn51-stability.md
@@ -71,6 +71,22 @@ Two ASUS PN51-E1 mini PCs (Ryzen 7 5700U) purchased years ago but shelved due to
 - **Conclusion**: TSC is genuinely unstable on the PN51-E1 platform. HPET is the correct clocksource.
 - For virtualization (Incus), this means guest VMs will use HPET-backed timing. Performance impact is minimal for typical server workloads (DNS, monitoring, light services) but would matter for latency-sensitive applications.
 
+### 2026-02-22: BIOS Tweaks (Both Units)
+
+- Disabled ErP Ready on both (EU power efficiency mode — aggressively cuts power in idle)
+- Disabled WiFi and Bluetooth in BIOS on both
+- **TSC still unstable** after these changes — same ~3.8ms skew on both units
+- ErP/power states are not the cause of the TSC issue
+
+### 2026-02-22: pn02 Second Freeze
+
+- pn02 froze again ~5.5 hours after boot (at idle, not under load)
+- All Prometheus targets down simultaneously — same hard freeze pattern
+- Last log entry was normal nix-daemon activity — zero warning/error logs before crash
+- Survived the 1h stress test earlier but froze at idle later — not thermal
+- pn01 remains stable throughout
+- **Action**: Blacklisted `amdgpu` kernel module on pn02 (`boot.blacklistedKernelModules = [ "amdgpu" ]`) to eliminate GPU/PSP firmware interactions as a cause. No console output but managed via SSH.
+
 ## Benign Kernel Errors (Both Units)
 
 These appear on both units and can be ignored:
@@ -84,8 +100,8 @@ These appear on both units and can be ignored:
 
 ## Next Steps
 
-- Monitor both units for stability over the next few days
-- If either freezes again, try disabling unused hardware in BIOS (GPU, WiFi, Bluetooth, audio)
-- If still freezing, may be a hardware defect
+- Monitor pn02 with amdgpu blacklisted — if stable, try the less impactful `amdgpu.runpm=0 amdgpu.dpm=0` kernel params instead
+- If pn02 still freezes without amdgpu, likely a hardware defect on this unit
+- pn01 continues to be stable — keep monitoring
 - Once stable: add second RAM stick back to pn02, reinstall with NVMe
 - Evaluate for Incus hypervisor use (see `nixos-hypervisor.md`)