Have you tried removing the checkmark from "use graphics processor" in the Lightroom preferences?
yes, i tried with and without. Now im doing to try to make for different folders different previews, one standard one 1:1 and one advance previews
Sorry, I have no other suggestions. I have not noticed any speed changes on my computer. But I know that a lot of people are expressing the same concerns that you are.
8 GB RAM
Intel integrated graphics (no special graphics card)