My Dell Rugged 5424 behaves normally on battery, with the CPU running around 3900–4200 MHz, although the batteries make a buzzing noise. About 15 seconds after connecting AC power, the CPU becomes capped at roughly 400 MHz and the buzzing stops. Charging is also unreliable and the batteries sometimes continue discharging while the laptop is plugged in. Both batteries report poor health.
The issue occurs in both the UEFI and Linux, so it does not appear to be software-related, and the CPU stays cool at around 46–48°C. Disabling Intel SpeedStep makes the CPU run steadily at about 1900 MHz on both battery and AC, but it no longer boosts. Disabling C-states has no effect. What could be causing this, and what should I check?
1 Answer
This strongly suggests the laptop is detecting a power-delivery problem and applying an emergency CPU limit. Even with an OEM 90 W barrel charger, the adapter may be failing, the DC jack or charging circuit may be damaged, or the system may not be correctly identifying the adapter. Dell laptops can heavily throttle the CPU when the charger is missing, under-rated, or not recognized.
Try a known-good Dell adapter with the correct wattage and plug, then check the adapter identification and charging status in the BIOS. Also inspect the charging jack and cable for damage. Since both batteries are reporting poor health and charging is inconsistent, the batteries or the laptop's charging circuitry may also need replacement. The fact that it happens in the UEFI rules out normal Linux power-management settings.
It is not a USB-C charger; I am using the original Dell 90 W barrel-style adapter. I will check whether the BIOS recognizes its wattage and try another known-good adapter if possible.