GTA 4 lag!!!

either your gpu isn't getting enough power (possible since you got some crappy brand PSU) or your game isn't actually using the GPU at full capacity

why is chieftec a crappy brand? the PSU has 20 amps on both 12V rails

Well actually i ran a stress test with furmark with 8X MSAA and 1920x1080 resolution and the test was completed successfully with no shutdown. average fps was 25

What's your CPU then? compare your settings to what you had before, might be bottlenecking there and holding the GPU back.

Chieftec is a brand that I'm hearing about for the 2nd time, and I haven't seen any reputable reviews stating that they are good. Just because it's got 20a written on the label doesn't mean that holds true.

regardless, check the utilization on cpu and gpu. check to make sure you don't have some power management software limiting the performance (set windows power to full performance). GTA is CPU bound, so it wouldn't surprise me if your CPU is overstressed

hehe that's what i'm afraid of   my CPU is an AMD Athlon II X3 455 CPU 3.3 GHz
though i think its a bottleneck or just the CPU can't handle the game that well. but its kinda weird because all other games run fine even battlefield 3 ran perfect. and about the chieftec brand it may not be popular in U.S but here its one of the best brands we have. this 500W PSU cost me 50$ and most 500W psu's are 35 to 40$

Best answer selected by Lazar_99.