Thunderbolt 4 and Backwards Compatibility

[eskimochaos]

I have been having a hard time verifying if Thunderbolt 4 is totally backwards compatible - all the way to DisplayPort 1.2.

I have two Laptops, one with two TB4 ports and another with two TB3 ports. I am able to connect my external Dell U3011 monitor to a USB-C to HDMI/DP adapter and a generic USB-C expansion hub via HDMI to my monitor with the laptop that has TB3 ports The laptop with the TB4 ports will not connect to the U3011 at all.

I took the machine with TB4 ports to Best Buy to try out a newly purchased USB-C to DP cable. It worked on only 1 out of 3 monitors that I tried. What gives? Why would the cable/device only work on one modern display? I thought it was the fact that my U3011 is approaching 11 years old; however, it appears there is something else that I haven't figured out?

Any help would be appreciated. Posting here since the LapTop section is ded.

 

[ssjwizard]

What brand notebook and what system chipset that can make a BIG difference in compatibility.

 

[eskimochaos]

What brand notebook and what system chipset that can make a BIG difference in compatibility.

Lenovo Thinkpad P1 Gen 5 with a 12800H and RTX A3000.

When connected USB-C to DP to the monitor, when I hit detect monitor in Windows, the monitor wakes from sleep but does nothing else.

I am pulling my hair out....not much left.

 

[eskimochaos]

FWIW I did a fresh install of Windows 11 and all is well in the world. I was at my absolute wits end.....

 

[ssjwizard]

Cool glad you got it sorted!