I’ve had similar results, I was not not successful. I tried two things.
- I edited the Setup section in the bios with ru.efi (*this was a bit of a pain, more below) by setting the values for one of the IOUs to 0. Truenas did not see any more Root Ports beyond the three hanging off that CPU. (2 x16s, and 1 x8)
- Using ru.efi, I edited the register address for bifurcation based on the intel cpu register spec sheet for my processors. (see [Guide] - How to Bifurcate a PCI-E slot - #127 by twochannel) I thought I was on to something with bit 3 to enable bifurcation and then 2:0 to set the config, but that didn’t work either. I was careful to continue booting vs restart since I’m sure these registers would be overwritten on boot.
*I had to use an older version of ru.efi to get it to run, version 5.32.0423 worked for me. The newer ones would hang at execution once the bytes started to load.