Acer Aspire E5-575G the processor runs at 480 MHz, instead of the declared 2000 MHz

bought a new laptop, then installed windows 10, I do not know why the processor runs at 480 MHz, instead of the declared 2000 MHz? Processor is Core I3-6006U (2.0 Ghz, 3Mb L3 Cashe). Reinstalled Windows 10 on Windows 7 the problem did not dare.