According to Osho, nirvana first extinguishes the mind—emptiness is realized while the body still lives—so an enlightened one may continue acting, usually out of compassion, despite a subtlest residue of being. With mahanirvana, at the body’s death, even that residue dissolves: sovereign, supreme emptiness, invisible to ordinary eyes, remains. In Krishna, this union of nirvana and mahanirvana is simultaneous; in Buddha, sequential.
First your thoughts end but you still live and help; later, when the body dies, even the last trace of ‘you’ melts into total peace.