We propose a novel real-time physically-accurate simulator for long flexible cable manipulation. We first discretize the cable into multiple rigid link segments, each with complementarity-based contact model and inter-segment compliant coupling; and partition the cable into a number of subsystems, each composed with a number of consecutive links. We then formulate the inter-subsystem consistency constraint as a certain analytical condition among the inter-subsystem coupling and the contact impulses; and solve each subsystem dynamics in parallel with the contact model together with this consistency condition in an iterative manner, achieving both the speed and the accuracy of the simulation. A novel post-regulation scheme is also proposed to further speed up the simulation. Experimental validation/demonstration are also performed to show the theory.