GPU usage up and down

[yahfz]

Hi, i've upgraded my video card from a gtx 560 ti to a 670, since then, i've been getting some random gpu usage for exemple (crysis3):
If i start running the fps drop along with the gpu usage. If i start look around doing a 360º my gpu usage goes to 99% to 66% then back to 99%, which is awkward because if i stand there without moving my camera the gpu usage stands at 99%.
My english is kinda bad, so i apologize for that.
PC:
GTX 670 Power Edition
Core i5 2400
8GB DDR3
Corsair CX430

 

[Silverbear]

The GTX 670 requires a 500 watt PSU or higher, with your PSU it's most likely unpowered and can't use it's full potential.

You should get something like this:
http://pcpartpicker.com/part/evga-power-supply-220g20750xr

It's 750 watts, so a little more than what you need, but it will last a long time and leaves space for future upgrades like a better CPU.

 

[yahfz]

My psu is fine as long as i dont overclock my card.Gtx 670 requires 30A in the 12v line, my psu has 32A. Its the new version.
I found the solution, my cpu is the bottleneck in crysis 3. Thank you for the help tho, i'll be getting a better psu later i just upgraded my card no cash yet =(