Is this normal for a R9 380 Nitro?

[PDQ89]

I have a R9 380 Nitro OC edition overclocked to 1136/1554 with a FX 6200 overclocked to 4.41. When I run Heaven benchmark I get a 27 FPS difference between 1440x900 and 1920x1080, it just seems like a huge difference to me, is the distance between 900p and 1080p really that far?

 

[burgessanthony]

It's 30% more pixels (head maths) so a fair difference

 

[greens]

https://lh4.googleusercontent.com/xkhn8rrZfXkVvP6UUiziCcRyFf774uaU2qWrDshGanDKjrpHWaXXvdovFnvo9jOtnuJqZ06EAklQ4_rNTqGP0RsRqLqHnM3q53Xw7mHCcoL5i2aoUnc0VDY_xw

It is a huge difference when you consider the actual number of pixels being rendered.