it could be the 650 being slow period, and the Nvidia drivers acting up as usual. ever since the release of Windows 10, Nvidia's driver support just went down the toilet.
As for Windows not liking GTA V? it's not. GTA V runs surprisingly great. even for a console port. which makes sense, they did release it a year later after the consoles got it. I've personally haven't had an issue with GTA V at all.
though realistically, if you rolled back drivers and ran it in compatiability mode, and it's still acting the same. it's most definitely the GPU.
So when i had my dual core i3 running with my 650 that was an ok combo, but now that i have a beefy i5 and my 650 its just not compatible and is it bottlenecking to the point where it wont run games?
The funny thing is it lags sometimes in windows too
Also as we speak my nvidia drivers are crashing and recovering every minute
Like I mentioned Nvidia's drivers support after Windows 10 went into the toilet. a lot of people have been complaining of issues, and some seem to think it's fine. as for the i3 vs the i5 thing. you should of definitely saw a performance boost.. though not by much though. like 5 or 10% at the most.
As for the compatibility thing you're mentioning. there's no bottleneck at all. it could just be the Nvidia drivers acting up.
have you tried reinstalling GTA V though?
Also try everything the guy below me recommended good sir.
Remove NVIDIA drivers, see if there is an NVIDIA software cleanup tool online and run it
Reboot without NVIDIA drivers.
Download latest, install
Reboot
Try game again
If that doesn't work. Rename your steam game folder, redownload the game over night and see if the new install works better. Happened to me on 1st install when game came out, some files were not correct or something.
Also if your machine is throttling, get evga precision from the evga website and crank up your GPU fans to 100% and your CPU fan to 100% and give the game a run.
Somethings wrong with my GPU for sure, i dont know what the problem is, most likely the driver but i dont know how im gonna fix it currently running off no driver installed