I got a brand new RTX 2060 a few days back and replaced it with my old GTX 660 but I am not receiving the correct performance as i'm only getting about a 5% boost in frames. I have installed the latest drivers and the game I am using to test my fps is rust. I am currently running it on Super Potato on the highest settings receiving only 40 frames previously receiving about 35 with my GTX 660. I'm also pretty sure that my CPU isn't bottle necking as it doesn't go past 40% along with my GPU. I am also running the resolution at what is needed and still don't receive a big boost in fps on many other games.
Here are my pc specs:
Graphics Card - NVIDIA RTX 2060 EVGA
CPU - Intel Xeon E545
Power Supply - 600 watts power supply
RAM - 22 gigs
64 bit
Windows 10
System Bios - 60KT44AUS
Nothing is overclocked
If there is anything else you need to know ask me.