hetzner-ex101: limit maximum frequency

hetzner-ex101: limit to 4.5Ghz

modules/hetzner-ex101.nix

@@ -1,8 +1,32 @@
-{
+{ pkgs, ... }: {
   # Enable raid support specifically, this will disable srvos's
   # systemd-initrd as well, which currently is not compatible with mdraid.
   boot.initrd.services.swraid.enable = true;
   systemd.services.mdmonitor.enable = false;
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
+
+  # We are not limited by zfs, so we can use the latest kernel
+  boot.kernelPackages = pkgs.linuxPackages_latest;
+
+  # looks like the Intel i9-13900 draws too much power and crashes the system
+  systemd.services.limit-cpu-freq = {
+    description = "Limit CPU frequency to 4.2GHz";
+    wantedBy = [ "multi-user.target" ];
+    after = [ "systemd-modules-load.service" ];
+    # Some cores do have a scaling max freq less than 5GHz, so we need to
+    # check for that or else all cores will run at 800MHz
+    script = ''
+      #!/bin/sh
+      for f in /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq; do
+        old_val="$(<"$f")"
+        if [[ "$old_val" -gt 4200000 ]]; then
+          echo 4200000 > "$f"
+        fi
+      done
+    '';
+    serviceConfig = {
+      Type = "oneshot";
+    };
+  };
 }