Hi, I have a 75hz Samsung monitor but I can't get it to run at 75hz, I've tried changing the refresh rate in settings, to no avail. also, my HDMI cable shouldn't be the problem as my brother uses it for his pc and it runs at 75hz just fine. it may be the gpu as its an old hd 4890, but I've tried it with my APU too, it could be because my APU is not 75hz compatible but I've never heard that being the case before. my motherboard could also be the problem but I'm not sure, any help is appreciated, feel free to ask for more details