I forgot to back up my AppleHDA before installing a non-DSDT patch, and now I'm trying to get it working with DSDT patches so I can have both onboard sound and HDMI audio. I had both working fine with VoodooHDA, but it didn't work with my microphone.
My motherboard is an MSI Z77A-GD65, which doesn't appear to have any patches designed specifically for it.
EDIT: I am an idiot. I just needed to use my optical cable properly. It helps if you remove the little rubber caps from the tips first.