First tell one thing what do you want to do to get marks above 8.5. I also scored 8.64 in 6th semester. I don't know about you but whatever your destination is, 8.5 or 9.5 is totally meaningless as far as competitions (like GATE, Campus placements etc.) are concerned. I strongly recommend you to not study for excellent marks. Try to build a concept in your favorite subject(s), & try to study for competitions. As far as result is concerned, Just maintain your result constant throughout all the 8 semesters.