Is it core or memory controller that throttles to 20-30%? cuz my gtx 850m memory controller throttles to that while gpu load and clock stuff stayed normal at boost clocks. It throttles at random temps, sometimes at the exact 57c, 60c, 63c which is rather low imo.
at some point i've able to bypass the weird "throttling" point by replugging the battery, it went 75c stable without any throttling. then after a reboot it went back again and i've never been able to bypass it anymore. been trying to bypass it again, probably because i've used some weird driver for another laptop which did bsod on my laptop or something before replugging the battery.
also been searching for the vbios with mmtool on the bios dump but i didn't seem find any :L