[Bug Report] XPS 9300 screen brightness blink/flicker

Hi,

I am posting an issue regarding to my xps 9300 screen brightness flickering. I noticed that when I stress the CPU by opening couple of web pages in Chrome browser, the screen's brightness would flicker; quickly dim by like 10% and come back to normal, and repeat this couple of times. I have a video recording showing this problem here:

https://drive.google.com/file/d/1HlRyw97X21gPDm89mmNGlvE6to7nO1dY/view?usp=sharing

this video was recorded by iphone 8 plus with ProCam app, under 720p 240Hz, constant iso and shutter speed. Without any post processing. notice the moment i open my email in the browser, the screen flickers couple of times. and also the task manager indicates a CPU usage spike during such period.

I did two more experiments. Experiment 1: In bios, I turned off "intel speed step" and "intel speed shift" features to limit the CPU to ~1.3GHz. Open the same web pages couple of times, the problem is gone. Experiment 2: enable "intel speed step" and "intel speed shift", but using 3 cores. the problem can also be resolved.

Now here is my assumption: when CPU with 4 cores were stressed and attempted to boost frequency, it suddenly draws high current, then causing a voltage drop on the screen back light. Hence causing brightness flickering/unstable.

I have contacted Dell and they actively helping me solving the issue by sending technician to my house and replaced my screen assembly and the mother board. However, the exact problem persisted after the replacement. BTW, my machine is i7+16g+512g+1080p_non-touch. 

So my friends, please try to observe if your machine have the same issue and leave a comment below. I wish the problem can be resolved by BIOS update, and it's not a design flaw. Dell is asking me to send the unit back for a further exam, but I do not know if it can be solved.