PC Engines system board schematics

PC Engines hardware may be the most "open source" hardware available on the market. Not only you are getting full access to the source code of the bios, but also you get full access to the hardware schematics. When something breaks, which almost never happens, you can read the schematics and figure it out for yourself.

 

APU3 board schematics

 

APU2 board schematics

 

APU1 board schematics

 

Coreboot BIOS

You can find the latest version of the bios source code here: https://github.com/pcengines/coreboot