Inconsistent FPS with new computer with the same old graphics card

[Ouroboros158]

I recently finished building my new computer 3 days ago. Every part of my computer is new except for the gpu (Radeon XFX 5770) and dvd/cd reader. After playing games, I noticed that my graphics card is not running as well compared to my older computer. At the moment when I tried to run SC2 in medium settings it would average about 40-50 fps and then dips to 15-30fps. This is unusual because when I played on my prior computer on medium settings, it would average 100 fps and it would only dip around 80ish when it goes into the late game. Due to the inconsistent fps, I tried playing on all low settings for a while. On this settings it averages 80fps and usually dips to 30fps. Recently, the frames would even drop to 1-5 and get stuck at this point when I engage in a battle. These inconsistent FPS also occur in other games such as Dota 2 and CS:GO. I have no clue what is wrong, but I did some temperature checking and the GPU idles around 52 and goes up to 65-70c when gaming. I even checked the CPU and it idles at 12c and goes up to 31c when gaming. So I have basically no clue what is wrong. My only assumption is that the gpu is being bottlenecked by the newer cpu. What are your thoughts? For your information, I did not overclock anything. In addition, I have the video card installed on the PCI_E2 slot which was recommended by my motherboard's manual. The only thing noticeably strange is that the GPU usage hovers only around 40-60% during gaming.

New Computer

Motherboard - MSI 970a-G46
Power Supply - Antec 520 HCG
CPU - FX 6100
RAMS - G.SKILL Ripjaws X Series 8GB (2 x 4GB)
Graphics Card - XFX 5770

Old Computer

Motherboard - Gigabyte EP43-DS3L
Power Supply - Antec Neo Power 550w
CPU - Intel E8400 duo core
RAMS - GSkill 4gb (2x2)
Graphics card - XFX 5770

 

[902]

your gpu could be bottlenecking your system idk i have no idea, try new drivers. have you cleared all the old ones. are you using the same hard drive? is your gpu running at good temps?

 

[Ouroboros158]

Yes, I have tried the latest drivers for both my motherboard and and graphics card. I am not using the hard drive and both the GPU and CPU are running at good temperatures. GPU is running at 55 c idle and about 65-70 when gaming.

 

[902]

have you changed your monitor? a higher res could be the problem?