Hi all, P55 motherboard owner here. As you may guess owners of this motherboards have major USB issues that still haven't been fixed (yet, i hope). Issue is simple: USB is not working properly, you can't do fresh installation because you can't use keyboard or mouse. Yet you can upgrade your current Yosemite and you'll start to have same issues, so you can't use the OS at all.
When there was a public beta, i've managed to use my DSDT that fits perfectly to Yosemite (Everything works fine with it), but it isn't working with El Capitan, and i've had 1 or 2 USB ports working after all. I believe there is a way to make all USB ports working, but where to edit/patch something and how? Is it something to do with DSDT or the kexts?