Since kernel 6.15 or maybe earlier:
the grub-parameter amd_pstate.shared_mem=1 amd_pstate=active
is needed for clocking down to minimal frequency.
amd_pstate=passive does not change any think (checked with cpu-x)
New driver amd_pstate-epp used by newer kernels afaik…
there many changes on amd-pstate on end 6.14.9 kernel and new series 6.15
can you use : amd-pstate ( no more amd_pstate.share_mem=1 )
UEFI up to date for your UEFI motherboard version
CPPC active
you can without option , you should see
amd-pstate-epp , with scheduler powersave_perfomance
if you try with
amd-pstate=active or passive or guided, you will see older scheduler ( schedutil , balance , perfomance and powersave )
Are you sure that is you set amd_pstate=active it doesn’t enable the new amd_pstate_epp? Because it does here. I need it to be passive to get the classic amd_pstate.