get another ram (make sure that it has the same latency, size, brand and speed) to make 8 gb of ram.
and your 470 has only 1gb gddr5 vram. bf4 can't handle it though.
and change also your cpu. try getting an i5 3570k or i7 3770k or, if you have some money there, get an i7 4770k (or i5 4670k) and a new motherboard also (i recommend msi z87-g45 gaming or gigabyte ga-z87x-ud4h)