Based on coarse grained simulations of a specially adapted model for bisphenol-A polycarbonate (BPA-PC) we generate by inverse mapping, the reintroduction of chemical details, well equilibrated all-atom conformations and time trajectories of dense polymeric melts for up to 7.8 µs. This is several orders of magnitude more than any direct all-atom simulations have reached so far. These polymer melts contain up to 68600 atoms in = 100 chains of molecular weight = 5217. By comparison with short all-atom simulations we show that these trajectories are physically meaningful, providing us with a powerful tool to compare long time simulations to experiments, which probe specific local dynamics on long time scales, such as NMR relaxation.