Z-clv vs cav

What determines when the NEC3500 uses the above 2 writing strategies :confused: I have used the same media Yuden000T02 and burned at 16x with unofficial 2.17 firmware and TDB 2.18 fast firmware and have gotten 2 different write graphs on cd dvd speedā€¦just curious. I always thought the NEC3500 were zonal constant linear velocity(z-clv)

nopeā€¦ its CAV @16x =)