i've read all the posts, thank you to everyone, especialy to exnihilodub.
I've been 4 days in a row trying to fix this problem (constant spikes from 724 to 270 mhz during 0,1s or so). i've tried everything on this forum and others, re-format, oc,uv,fixed volt, turboboost, c1e, prochot, NVinspector, throttlestop..cheking temps on both gpu cpu... nothing did it.
You said something can't go to 50C, so i've decided to open my mac and point two fans at the mainboard without any software on ecxept gpuz for monitoring.
IT WORKED!!! the core and mem frequencies kept at 900/2500 all the time when playing payday 2 at 70-75fps,about 20-30min. i took the fans out and in about 10-30 secs it started to go 724 and a few seconds latter the f*$«%*# throttling beggan even with gpu at less than 70C and cpu less than 75. (then i tested with realtemp and cpu was fixed at 2ghz, from 95% in win energy preferences i think)
I can test everything you want to take out some theories, like keeping gpu and cpu at higher temps(80-90) and keeping 900/2500 with extra fans on. ask for anything you want. tomorow ill do more tests.
I'll try to get some friends infrared distance thermometer to find witch component needs some mini fan or passive dissipator.
http://www.clickbd.com/global/classified/item_img/1090077_0_original.jpg