The national name check is conducted by FBI, which is said to be kicked off by FP, when FBI has received your fingerprinting. Then they use your fingerprints and other biographical information to check your record against their central database system. If no match is found by the computer, then the result comes out automatically and electronically. Otherwise, once a link is found, human being has to be involved to solve that link, and field offices may be involved if file links to them, then the processing time is extremly unpredictable.
So the result is, your name check could be done within a matter of days, or be pending for years.
Good luck!