In this work, we study an EPR-IV system for high density digital recording and compare it to the PRML recording system. A combinatorial optimization technique that uses the simulated annealing algorithm in conjunction with a descent method is employed for optimization of partial response (PR) equalizers. The gradient algorithm to track variations of timing phase for the EPR-IV channel is investigated. Also, a generalized Viterbi algorithm is used for detecting the EPR-IV system. Simulation results demonstrate that at high recording density, a coding gain over the PRML system can be obtained for the EPR-IV system with a comparable complexity.