Lenovo laptop hdmi, Windows 11 no display on dummy plug but ok on external monitor?

[edidcru42]

Hello,

Got a weird situation.

Until now, i've been using fake monitor dummy plugs on vga/dvi/hdmi/displayport with Windows 10/11 successfully on PC/laptops, along with CRU utility.

I've got a Lenovo P1 G7 laptop which has built-in HDMI 2.1 connection. I tried both hdmi 2.0 and 2.1 dummy plugs on it, and Windows 11 does not detect a new display. Perhaps a bad hdmi port on the laptop? I connected up a hdmi external display, and i get new display. Maybe the dummy plugs are bad? I tried them in different laptop/PC combination, and each show the new displays in Windows 11.

What's going on here?

I connected up the port replicator, which has hdmi port on it, to the laptop. Plugged in the same dummy plug, and Windows 11 shows new display.

Seems from isolation that this Lenovo P1 G7 laptop's built-in hdmi, is good, but hdmi dummy plug will not work (for some reason). Well, this is first failure for me in such situation.

Anyone run into compatibility issue on a particular laptop hdmi port with hdmi dummy plug that is known good and works in other latop/PC's hdmi 2.0/2.1 ports?

What could be so unique about the Lenovo P1 G7's hdmi port?


Here the hdmi external display is connected to the laptop's hdmi port (i do have connected to laptop, two dummy DisplayPort's, total of 4 displays, 1, 2, 3 and 4)



Unplugged the external hdmi display, plugged in hdmi dummy plug. Windows 11 does not detect the new display. Windows 11 only has displays 1, 2 and 3.




Thanks!

[ToastyX]

What are the EDIDs on the dummy plugs?

[edidcru42]

(06-24-2025 01:54 AM)ToastyX Wrote:  What are the EDIDs on the dummy plugs?

Here's the screenshot from CRU for the hdmi dummy plug. When plugged into the Lenovo laptop, no display is detected. But when i plug it into some other laptop's hdmi port, new display is detected.




Here's screenshot of external HP Z24i G2 monitor plugged into the same Lenovo laptop's hdmi port, and i get new display from making that connection. But using dummy plug on the same hdmi port, no new display. I tried also copy and paste from HP monitor to the dummy plug, save, reboot. Same result, no display is detected from Lenovo laptop when dummy plug connected to the hdmi port. The graphics card is Intel ARC adapter in laptop.




What's even more strange is, using the same hdmi dummy plug on the Lenovo laptop's docking station which has hdmi port, new display is detected. What........

But if i use the same dummy plug in the hdmi port on the laptop itself, no display. Connect external monitor to same hdmi port, i get display. Urgh...

Thank you.

[ToastyX]

I need the EDID, not a screen shot. Export a file for each dummy plug and post them here.