We analyze elliptic flow from SIS to RHIC energies systematically in a realistic dynamical cascade model. We compare our results with the recent data from STAR and PHOBOS collaborations on elliptic flow of charged particles at midrapidity in Au+ Au collisions at RHIC. In the analysis of elliptic flow at RHIC energy, we find a good fitting with data at 1.5 times a scaling factor to our model, which characterizes that the model is required to have extra pressure generated from the subsequent parton scattering after the initial minijet production. In energy dependence of elliptic flow, we notice re-hardening nature at RHIC energies. Both these two observations would probably imply the possible formation of quark-gluon plasma.