Thanks for fast reply guys! Really appreciate it.
Today I made some tests and with below setups I could manage to make it works without any trottle. The thing is: Temperature still above 80C. So looks like the problem maybe is high temp + high voltage. I will make more tests. But this is a very strange behaviour. Really hard to understed these modern chips lol
1035 Core Clock
1499 Memory Clock (i can reach 1600 easily, but I read a while ago that it's not recommended since timings changing and performance could be decrease)
Idle temp is something between 36~40C. To reach 80~85C its taking something about 5 or 6 minutes. Case is not the best, but I have 2 90mm in the front with positive pressure, one behind and one above, both negative pressure. This is the case: https://29028l.ha.azioncdn.net/img/2017/11/produto/64251/gabinete-gamer-bluecase-mid-tower-bg-015.jpg
And yes, thermal compound is relatively new (Artic Silver 5 ~ several months ago).
About fans, well, long short history: its not original. The VGA model is Gigabyte G1 Gaming.( https://i.ytimg.com/vi/vGSWFutKARo/maxresdefault.jpg ). But a year ago something happens and boom, coolers stopped from work and same for PWM on the VGA board. So I bought a faulty r7 370 card for 5 bucks and i'm using these fans (Asus Strix https://encrypted-tbn2.gstatic.com/shopping?q=tbn:ANd9GcSUpbzghoZ9WQQCsy5Va1a5k8BMMnmyHH4ziKnELaqK9UtCOS9skK61nCYsoJ18Xa5LbH0o7OVR_ozw_IPNtKx9FFGCQEjp2g&usqp=CAE ), but keeping the original Windforce heat sink from Gigabyte G1 Gaming. I don't know if i could change the whole thing because if you look well, the Asus Strix heatsink doesnt cover memory and other things. A advice here would be nice too because I think it would be much much better if I could use cooler and heatsink from Asus Strix.
Anyway, my temps was always something about 75C on Windforce and since this needed change it's reaching 80~84C with 100% fan speed using FanSpeed software.
RadeonPRO by Japamd, right? This is what i've used when I buy it years ago and yes, it works to block clocks! It was mandatory to play FIFA without stutter! I will definitely will give I try, I completed forget about this sofware! Clockblock doesnt work very well, clocks are reduced depending on temps too.
Answering the question,
Gigabyte G1 Gaming R9 380 4GB
BIOS version 015.049.000.002.000000
Like I said at the begining of this post, It's looks like Gigabyte made something really strange on this BIOS. High temp and High voltage = trottling. I will made more research too.