AMD A4-5300 with Radeon HD7850 Bottleneck?

[rawkid300]

My computer specs are as follows:
AMD A4-5300 APU 3.4GHz
Sapphire Radeon HD7850 2GB
4GB DDR3 Ram (1333 MHz)
500 GB SATA Hard Drive
Windows 8.

Here's whats happening:
-AC4, I play ac4 and get smooth 30 fps when near seas or looking up at sky, when im in town my fps drops to 10-16. I ran fraps to see the fps difference, i put EVERYTHING on ultra high, 16 fps... i put EVERYTHING on low, in the same spot, 16 fps.

-Far Cry 3, On far cry 3 i get around 20-25 fps, which is not too bad. I put all options on ultra high and get the EXACT same fps on very low.

I play these game through Steam/Uplay.
Now I want to know what's causing the problem and any possible fixes, if not then I wish to know what possible upgrades might help fix the problem. Please bare in mind I do not have a job so i will need to save up money, therefore try keep budget as low as possible.

Thank you.

 

[ewok93]

That would be a bottleneck, I would save up for something like a 6300 and an Asus M5A97 R2 LE.

 

[Gathorisx]

Your processor is bottlenecking your GPU you should upgrade your processor and motherboard either to a FX8320/6350 And a AM3+ Board like the M5A97 R2.0 or a new FM2+ motherboard and a new A8 7700 or A10 7850k

 

[rolandzhang3]

The cheapest option you have would be to get an Athlon 750k or 760k