[SOLVED] No display when putting my old GPU into a fresh build

[IamTheNoa]

When i put the GPU in my pc neither the GPU or the IGPU will display anything, when i take it out my IGPU works.

PC specs:
MB:GIGABYTE B560M-DS3H
CPU:Intel Core i5-11400
GPU:MSI GTX 780 Lightning
PSU: LC Power 600W

*Note:
The ram is correctly placed, i tried adjusting them,
The GPU is getting connected for external power,
The GPU sits correctly in the PCIe slot
Everything except the GPU and PSU is brand new
When i plug in my old 8800 GTS it works which makes me think it's a problem with the PSU
The GPU is getting power from one 8 pin cable which is extended to have another one which might be the issue
The GPU and PSU worked correctly in my older pc

 

[geofelt]

Your GTX780 may need a legacy/uefi bios to run.
In your motherboard bios,there is likely a setting to allow legacy devices.
It might be called CSM.