On MacOS Low-Power mode in the Power section of system settings disables turbo-boost. On Linux
echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
does the rick. Note that this is not the same as power-saving mode in Gnome settings.I have found that for heavy C++ compilation that lasts for many minutes the slowdown was about 20% on my ThinkPad X1 laptop. The big plus is that it made the laptop almost silent.