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IGPU disappeared !

Posted: Tue Nov 16, 2021 2:33 pm
by promeneur
Linux openSUSE 15.3

i get an intel igpu and an nvidia gpu.

today i decided to unplug the monitor from igpu and to plug it to nvidia gpu.

i restarted the PC

Then I opened a session and launch fah-control. The slot corresponding to the igpu has disappeared !

here is the log

13:27:51: GPUs: 1
13:27:51: GPU 0: Bus:1 Slot:0 Func:0 NVIDIA:3 GK208B [GeForce GT 730] 692.7
13:27:51: CUDA Device 0: Platform:0 Device:0 Bus:1 Slot:0 Compute:3.5 Driver:11.4
13:27:51:OpenCL Device 0: Platform:1 Device:0 Bus:1 Slot:0 Compute:3.0 Driver:470.86

here is the old log

06:44:08: GPUs: 2
06:44:08: GPU 0: Bus:0 Slot:2 Func:0 INTEL:1 KBL GT2 [HD Graphics 630]
06:44:08: GPU 1: Bus:1 Slot:0 Func:0 NVIDIA:3 GK208B [GeForce GT 730] 692.7
06:44:08: CUDA Device 0: Platform:0 Device:0 Bus:1 Slot:0 Compute:3.5 Driver:11.4
06:44:08:OpenCL Device 0: Platform:0 Device:0 Bus:NA Slot:NA Compute:2.0 Driver:1.3
06:44:08:OpenCL Device 1: Platform:1 Device:0 Bus:1 Slot:0 Compute:3.0 Driver:470.86

Re: IGPU disappeared !

Posted: Tue Nov 16, 2021 4:29 pm
by aetch
You'll need to enter your bios and change the setting which enables your iGPU, it's lilkely set to "auto", you'll need to change it to "enabled".

This will involve rebooting your computer and spamming the "F2" and/or "del" keys while the computer is POSTing.

Re: IGPU disappeared !

Posted: Wed Nov 17, 2021 8:47 am
by promeneur
With.the Asus Prime 250M-A it is more complicate.

There is a feature "Allow to select a primary display" [*] when there are several monitors.

This is automatic, but by default it is disabled.

You have 2 parameters:

"primary display" set to "auto"
"CPU graphics multi-monitor" set to "disabled"

you must set "CPU graphics multi-monitor" to "enabled"

[*] if someone can explain this feature (I did not find any Asus doc)

anyway thanks

Re: IGPU disappeared !

Posted: Wed Nov 17, 2021 9:40 am
by aetch
I didn't want to get too specific as the multi-gpu settings are different between motherboard manufacturers.

On-board/iGPU/Integrated Graphics/<whatever it's called now> is available on most, but not every, motherboard.
Typically the on-board graphics gets disabled when a discrete graphics card is plugged in.
In the past there would be a setting to enable/disable the on-board graphics card regardless of other cards in the system, that'll be your "multi-monitor"

Going further, you can pick the order (iGPU/PCI/AGP) which the system will attempt to use the graphics cards at boot time, that'll be your "Primary display".
It only needs one to work, the rest will be loaded by the operating system.
In your case, the system saw you had a monitor connected to the iGPU, loaded it and kept it on for the operating system to take over.
When you disconnected the monitor from the iGPU the system saw you no longer needed it and switched it off.
This does not happen with a discrete graphics card.

I hope that helps explain it.