[Help] F4-425 Pro (N350) — PL1/PL2 firmware values set ~2x above Intel spec, BIOS override doesn't propagate to OS/hardw

[vrouleau]

The N350 idles/runs at 90-95°C even under light-to-moderate load (e.g. Immich containers), occasionally triggering the thermal alarm. Investigated the root cause and found the firmware's power limits are configured well above Intel's official spec for this chip.

What I found:

Stock power limits (read via /sys/class/powercap/intel-rapl/):
PL1: 13,500 mW
PL2: 25,000 mW
Intel's official spec for the N350:
TDP / recommended PL1: 7W
Recommended PL2 ceiling: ~15-18W
Source: Intel ARK / Notebookcheck spec pages. The N350 is rated for 7W sustained — the shipped firmware allows nearly 2x that (13.5W) indefinitely, which is a significant mismatch for a chip in a compact NAS enclosure with a heatsink/fan combo sized for a 7W part, not a 15W+ one.
Tried correcting it via BIOS setup:
Set PL1 = 7000mW, PL2 = 15000-18000mW in BIOS.
Confirmed the values saved correctly (re-checked BIOS after reboot — still showing my values).
Performed a full cold power cycle (not just a warm reboot).
Result: the change did not propagate to the OS/hardware.
/sys/class/powercap/intel-rapl/intel-rapl:0/constraint_0_power_limit_uw still reads the original 13,500,000 (13.5W) after the BIOS change and cold boot.
Attempted to verify directly at the MSR level (MSR_PKG_POWER_LIMIT, 0x610) to rule out a sysfs/driver caching issue, but raw MSR access via /dev/cpu/0/msr is blocked with "Permission denied" even under sudo/root — likely due to a missing CAP_SYS_RAWIO capability in the TOS shell environment, which prevented deeper verification.

[TMjack]

Regarding the high CPU temperature you reported, you can lower it by adjusting the PL1 power limit in the BIOS. Follow these steps:
Enter BIOS, navigate to Advanced > Power & Performance > CPU Power Management Control > Config TDP Configurations > Power limit1, change the original value of 13500 to 12000, 11000, or 7000, then press F4 to save and exit BIOS.

Note: Values are in milliwatts (mW). Conversion: 13500 = 13W, 12000 = 12W, 11000 = 11W, 7000 = 7W.

[vrouleau]

This is what I did and it is set in the BIOS, but does not reflect in the TOS /sys/class/powercap/intel-rapl nor in reduction of CPU temperatures. That BIOS change did not change the CPU temperature behavior.Also I noticed at idle, the CPU is constantly being throttled:
vrouleau@terramaster:/# for c in /sys/devices/system/cpu/cpu*/thermal_throttle/; do echo "== $c =="; cat "${c}core_throttle_count" 2>/dev/null; cat "${c}package_throttle_count" 2>/dev/null; done
== /sys/devices/system/cpu/cpu0/thermal_throttle/ ==
78440
90024
== /sys/devices/system/cpu/cpu1/thermal_throttle/ ==
78440
90024
== /sys/devices/system/cpu/cpu2/thermal_throttle/ ==
78440
90024
== /sys/devices/system/cpu/cpu3/thermal_throttle/ ==
78440
90024
== /sys/devices/system/cpu/cpu4/thermal_throttle/ ==
12349
90708
== /sys/devices/system/cpu/cpu5/thermal_throttle/ ==
12349
90708
== /sys/devices/system/cpu/cpu6/thermal_throttle/ ==
12349
90708
== /sys/devices/system/cpu/cpu7/thermal_throttle/ ==
12349
90708
vrouleau@terramaster:/# for c in /sys/devices/system/cpu/cpu*/thermal_throttle/; do echo "== $c =="; cat "${c}core_throttle_count" 2>/dev/null; cat "${c}package_throttle_count" 2>/dev/null; done
== /sys/devices/system/cpu/cpu0/thermal_throttle/ ==
78465
90053
== /sys/devices/system/cpu/cpu1/thermal_throttle/ ==
78465
90053
== /sys/devices/system/cpu/cpu2/thermal_throttle/ ==
78465
90053
== /sys/devices/system/cpu/cpu3/thermal_throttle/ ==
78465
90053
== /sys/devices/system/cpu/cpu4/thermal_throttle/ ==
12353
90737
== /sys/devices/system/cpu/cpu5/thermal_throttle/ ==
12353
90737
== /sys/devices/system/cpu/cpu6/thermal_throttle/ ==
12353
90737
== /sys/devices/system/cpu/cpu7/thermal_throttle/ ==
12353
90738

[CursaYang]

Thank you for your detailed testing. We suspect this may be related to the device itself. Please provide temperature and test screenshots and send them to our technical support email (support(at)terra-master.com), along with a link to this post and your purchase order information.

[vrouleau]

Thanks for the reply. Support got back to me . The value had to be set in "Advanced" > "Power & Performance" > "CPU Power Management Control" > "view/configure Turbo options".

After that change the PL1 remains at 7W, at 100% at temp at properly stable a 100%. CPU freq at 1300 on all cores at 100% as per specs.



Maybe you should consider a firwmare change to set turbo PL1 at 7000. I suspect the 13.5W value was cut$paste from another of your models. Other people on reddit have reported the issue

[EriChan]

Thank you for your updated feedback. We will continue to monitor the situation and make ongoing improvements.

[DekkaR]

I've changed the PL1 value in the BIOS to 7000. Once I made that change, the NAS is indeed stable at a temperature of 60 degrees.

However, I'm noticing some strange behavior: even at 90 percent CPU usage, the temperature stays pinned at 60 degrees, but the frequency never goes above 1.2 to 1.3 GHz, when theoretically this CPU can reach 3.9 GHz.

So while I think setting PL1 to 7000 improves the situation, it feels like the N350 processor isn't performing anywhere near its full potential.

One value I haven't touched is PL2, which I've left at its default of zero. I'm not sure if you've tried setting it to 18000 or 25000, which is what Intel recommends. Intel says the maximum PL2 value is 25000, meaning 25 watts. I haven't made that change yet and kept it at zero. I might stop the NAS, make that change to 18000 or 25000 on PL2, and see how it behaves. Have you tested this yourself?