[SOLVED] Lower CPU performance on integrated graphics?

[DOGGO_Woo]

Hello!
I have a laptop that has a Core 2 Duo P8600 (old CPU, I know) that runs on the integrated GMA 4500MHD chip. While stress testing the chip, I found out that graphical performance takes a massive hit when both CPU and GPU intensive tasks are running (Furmark's stress test and cpu stress test). Furmark running only the graphical test (No fuzzy object) ran at 68 fps, while with the CPU burner also active, it reduced down to 40 fps.
Does anyone know the reasoning behind this? Here are the specs if they help:

CPU : Core 2 Duo P8600
RAM : 4gb DDR3 1066 mHz

 

[JWNoctis]

Integrated GPU from that era was still located on the northbridge (i.e. the chipset was still a set as opposed to a single chip, as it has been for about a decade).

While it doesn't have to draw upon the CPU's thermal and power budget, it still shared the same memory bus with that. Heavy demand from one will impact the performance of the other.