Inspiron 5502 CPU stuck at minimum clock

Hello,

we've purchased three Inspiron 5502, and all three have the same problem: the CPU clock speed is most of the time at minimum, not going above (circa) 0.4 GHz. We've upgraded all drivers and BIOS.

Of the three computer, one sometimes seems to not show the problem anymore, but its speed is not consistent for the same operation (eg. it can compile a C project at 3.8 GHz and at 2 GHz in the next try). Also, the problem can show up again after a system restart.

The BIOS is setted to maximum performance, we tried to replicate the settings of the "working" PC on the others but with no success.

Solutions posted in the community regarding the same or similar problem did not work.

I've personally called Dell'assistance, but they weren't able to solve the problem and invited me to call Software Assistance, which is not free even if those computer are new and with a valid warranty.

Do anyone have some suggestion on how to solve this problem? It's very frustrating to work in this conditions