Hi, Thx for your suggestions. People from customer care helped me replace the hardware so my problem was solved. But I still wasted lots of time on this, since the technicians could fix the issue in the beginning. 
Hello all, I bought my X17 (i7+3080) in June. It was a fanatic laptop and I loved it a lot. Last weak, I sent it back to factory because of the motherboard malfunction. They replaced it and sent it back. However, I found out that the CPU thermal is way worse than before. The stock laptop can score above 5300 in R20, but now it can merely score 4400. The temperature easily rises to 100 degree and thermal throttled so CPU wouldn't stay at 4.2G in 95 degree as before; instead; the frequency is 3.7G in 100 degree now. If I am right, this performance is no better than the last gen i7. I spent two hours with dell customer service and they refused to fix it. After being reviewed by some senior technicians, they believed that it is absolutely normal and the performance is within the "expected parameter". Is this means Dell regard their laptop is no issue as long as the laptop can still boot into the Windows? I spent over $3000 for this laptop and why I cannot get full performance of it?
My X17 coming back from factory repairs and the CPU performance drops 20%. DELL 
refused to fix it.