Just got myself an ASUS Vivobook X540MA, and the CPU (Celeron N4000) is giving me some trouble. When the laptop is plugged in, it behaves like normal and boosts up to 2.5 Ghz, and the machine's performance is ok. However, when I unplug the laptop, the CPU clock speed instantly drops to 0.79 Ghz (as reported by TM) and stays frozen, and therefore, the laptop becomes barely usable. Tried updating the BIOS, changed the power plan - nothing helped. Any tips? thanks in advance!