GTA V Lagging in 1080p?

[Kybz]

I normally play GTA V in 1280x720 and it runs smooth enough for gaming. However when I put it into 1920x1080 it randomly starts lagging SO badly unless I put all the settings on minimum. But when I put it in 1920x1080 it doesn't go over my vRam limit so I don't see why it should start lagging...

1920x1080
http://gyazo.com/68ea2d67ed038f859f95a1afe01e47c6
As you can see, it doesnt go over the limit but still lags...

1280x720
http://gyazo.com/717d830155399ccad874debce41cc9f3
It runs way smoother.

I know that in the 1280x720 one, the vRam is 200 less than the 1920x1080 one, but even if I lower other graphics settings so that the two vRam's are equivalent, the 1920 one will still be unplayable lag...

How do I fix this?

Specs:
AMD FX-6300
AMD Radeon HD 7700 Series
16GB RAM

 

[mmaatt747]

It's not lagging b/c of a lack of vram. The higher resolution requires more sheer processing power by your GPU