CPU frequency governor problem

Hi, sorry for the direct email but I=E2=80=99ve been unable to find a resol=
ution
to this in forums etc.  I have a laptop with a Intel i7-7700HQ CPU and am
running Linux Mint 18.  The frequency governor is set to performance but
it keeps on throttling down to 70% or even 50% and getting stuck there,
for example:

cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
70

I can=E2=80=99t find a way to get it to throttle sensibly i.e. lower the ma=
x
when required but revert to full speed when other conditions allow. I=E2=80=
=99ve
tried the ondemand and performance governors.

Any suggestions would be much appreciated.

thanks,
Ed