Discrete GPU FPS issue

Hi all...

I'm having Dell Inspiron 15 3521 running Windows 10 home. For some reason, I'm getting low FPS (9-11) on discrete GPU (AMD Radeon HD 7670M) compared to integrated GPU (Intel HD Graphics 4000) with FPS (36-41). I tried uninstalling through the control panel & device manager & reinstalling the updated GPU drivers (installing Intel than AMD & AMD than Intel) but nothing works.

Any help or information would be helpful.

The above FPS are obtained while running Dell SupportAssist specific device troubleshooting.

System Spec:

HDD: 500GB

Memory: DDR3 4GB

CPU: Intel i5-3337U

GPU: Intel HD 4000 & AMD Radeon HD 7670M (1GB 900MHz)