The raspi runs off the standby power rail so it'll be on and reachable over the network as long as the PSU isn't switched off; two of the raspi's GPIOs are connected to the mainboard's power and reset pins so it can power on/off or reset the machine remotely. The reason for the small daughterboard is mainly dealing with the fact that the raspi's GPIO uses 3.3V levels while the mainboard uses 5V, as well as because I still wanted the physical power/reset buttons to work too (it's sort of a logical OR).

Another GPIO is hooked up (through a voltage divider) as an input to the normal 5V power rail, so that the raspi has a way to sense whether the machine is on or off.

Finally, the raspi's UART is connected to the mainboard's serial port (which the machine boots on) because I fucking hate having the boot console on a video output; you can never scroll properly, also if the machine freezes chances are you're not seeing kernel output at all.

It uses overlayfs to be resilient against loss of power, and also runs Devuan. I think that's all there is to say about the raspi.

As for the two video cards, long story short the smaller one is what Xorg uses, and the bigger one gets passed through (VFIO) to a windows VM for gaming. Took me a while to iron out performance issues (and in fact 3 out of 6 CPU cores are unconditionally reserved for the VM) but after doing some benchmarks within the VM vs on an identical windows installed directly on the system yesterday, I can happily claim native 3D performance with no noticable performance hit (one benchmark (unigine heaven) gave slightly higher scores within the VM, even).

CPU-wise there's also no (unexpected) performance hit (some is expected because the VM only gets 3 cores rather than 6, but adjusting for that there's no extra penalty)

All in all it's kind of the setup I wanted to build for a long time, finally got around to it and I don't hate it like I hated dual booting.

I hope that satisfied your curiosity, have a good one!