I have a Laptop 13 (AMD Ryzen 7840U) (UEFI version 3.18) (Windows 11 25H2) which is used with an external monitor (lid closed) 80% of the time. My default Windows power mode is balanced.
I recently switched from Gigabyte M28U to Dell U3225QE. Both are 4K displays with VRR. The Gigabyte supports up to 144Hz and has a USB Type-C DP Alt Mode upstream; the Dell supports up to 120Hz and has a USB4/Thunderbolt 4 upstream. The cable I use is a 1m long USB4v2/Thunderbolt 5 240W cable from Ugreen.
The M28U provided just 15-18W of power over USB-C, so I usually plugged the laptop into the monitor and the Satechi 100W USB-C PD Wall Charger. The thermals were always okay, peaking at around 80°C.
The U3225QE provides up to 140W of power through USB PD EPR profile, but my Laptop 13 cannot take in more than 100W, so I guess the power input numbers should be exactly the same. After switching to that monitor, my Laptop 13 thermals became garbage when plugged into the monitor with its lid closed. It runs up to 80°C at idle and hits 100°C at load, which seems to be the firmware thermal limit.
I have had this issue ever since I switched from one monitor to the other. As a countermeasure, I am using Windows energy saver mode, which really helps to keep thermals between 50°C at idle and 80°C during heavy workloads. But that causes many different things to fail. For example, my usual Moonlight 4K 120FPS HDR stream stutters heavily in that power mode. Works perfectly when I turned it off.
I have made multiple screenshots over the last few weeks using Framework Control. I don’t remember every single thing that happened there, but there could be nothing running in the foreground except for Chrome, MS Word, or VS Code. Each time you see a plateaued 50°C, that is probably when I switched to and from battery saver mode.
And I would like to point out that I have not changed my use cases for the laptop with the switch of the monitor. Everything I do now, I did before on the old one, and nothing caused my CPU to go past around 80°C there. I never heard the fans spinning so loud before the switch.
Click here to reveal screenshots
That’s where I probably switched from energy saver mode then made a CPU stress test in CPU-Z:
That’s a funny one. I switched from energy saver mode then let my PC do whatever it wanted to do, and once it kinda cooled down, I noticed it spikes up like 5-10°C once I press the print screen button. So all those spikes are from pressing print screen:
As far as I remember, that’s when I noticed my fan is very loud while browsing Chrome and decided to check what is going on with thermals:
Bunch of other random screenshots:
And that is an interesting one. I decided to wake my screen, not even sure if the PC was asleep:
And this one is fresh. I once again tried to disable battery saver mode and after some time noticed the fan spins like crazy:
I believe this is either somehow related to USB4/Thunderbolt or a firmware issue, maybe both. Recent UEFI/BIOS firmware 3.19 mentioned something about fixing Dell U2725QE connection, which is exactly the same monitor as my U3225QE, just with a smaller screen. That’s why I think the firmware issue could be the root cause. So I will cross-post links to this topic in both UEFI/BIOS 3.18 topic and UEFI/BIOS topic 3.19 for my device.