Low Fps on 7770HD

[RaD1uM]

I just upgraded my graphics card from 9500GT to Gigabyte HD7770.
while playing dota 2 i am getting 30-55 fps where on this card i should be getting a 90+ fps without vsync
my resolution : 1600*900
specs :
cpu : Core 2 duo e7200
ram : 4GB DDR
mobo : intel dg31pr
psu : Antec EA 500

 

[cookybiscuit]

Its because your processor is extremely weak compared to whatever would have been used in benchmark tests you watched that get 90FPS.