determining the appropriate sata driver

[Ken Teh]

How does a system determine the appropriate sata driver?  Specifically, how 
does anaconda figure out to write

alias scsi_hostadapter ata_piix
in my modprobe.conf and to bind it into my initrd image?

I took apart boot.iso but didnt find anything "readable" that indicated how 
this was determined.

Thanks!

Ken