Having already one graphics card installed in my server I tried adding another one, but receive this error message and couldn't find anything in the system device where I thought I needed to setup IOMMU. None of the graphics cards work when both of them are put in the server.

Can anyone help me out how to fix this?

 

I can't guarantee I can help, but I might be able. First thing we need is lots more information. A diagnostics.zip file will include your hardware specifications and full kernel logs, which may make troubleshooting much easier. Having such a tiny window of logs, it's easy to miss other important factors, like BAR information, memory mappings and/or conflicts, or even just seeing that you have a chipset with a known errata for multi-GPU. Start the server, go to Tools, Diagnostics, then download it and attach it to your next post.

 

If you're unable to access the webui but can access it via ssh or terminal, log in and run the command diagnostics -- from there, pull the USB drive, put it in your computer, and drop the diagnostics.zip from the logs folder onto your next post.