It adds a new IOKit Personality, which is just a means by which hardware can be matched to a driver (
https://developer.apple.com/library...tual/IOKitFundamentals/Matching/Matching.html) . It doesn't replace anything within the AppleAHCIPort kernel extension, which is why i like this type of modification. It leaves the standard Apple kernel extensions alone. Also, when Apple updates these extensions in a future update (like 10.8.1), you won't have to repatch anything.
If you're using a DSDT, you can also
inject the correct device id in the DSDT and not need any kernel extension changes.