Why such a low performance?

Question

motherboards

I ran into a problem that was quite serious for me - a month ago, the computer simply did not turn on, giving 5 long BIOS sounds.
Googling realized that the problem was with the RAM, found that the first two slots did not work, before that everything worked in two-channel mode, 2 and 4 slots, at the moment it costs 3 and 4.
FPS has dropped tremendously in games, in the same CS me 40-50 fps, despite the fact that I have an i7 8700k and 1060 6 gb - when playing, nothing is loaded.
One of these days I will change the motherboard, and so, the question is, why did the FPS drop so much in games? Could this be due to the single-channel mode? I understand at 20-30 fps, but at 100-140?
I have DOTA at minimum 30-40fps! Please help, I don't know how to solve the problem...