AMI, Phoenix BIOS SDKs?

I’m just gonna throw this one out here in case anyone has any insight while I read about things.

For starters, let’s go back ten or twenty years. Most systems are running some kind of AMI, Phoenix, or Award BIOS at this point, but how are board partners/manufactures generating these binary blobs?

Is there an NDA’ed SDK that gets released/purchased by them for BIOS development? If I were a board manufacturer that wanted to implement some arbitrary x86 processor + chipset on a board, how exactly would I go about getting a BIOS configured for my specific platform?

And stretch goal, does that same procedure apply to newer UEFI firmware like the AMI APTIO package?

Will discuss in more detail but anyone around here familiar with this field?

So on further reading, it appears that at least AMI licenses out the source code as a reference package which you modify with your own initialization stuff and compile. Imma have to see if that’s leaked anywhere. I’m sure it has.