Service time distributions at computer processing units are often nonexponential. Empirical studies show that different programs may have markedly different processing time requirements. When queuing disciplines are first come, first served, preemptive priority or nonpreemptive priority, models reflecting these characteristics are difficult to analyze exactly. Available approximate techniques are often too expensive for parametric analysis. Inexpensive approximate techniques for solution of central server models with the above characteristics are presented. The results of these techniques are validated with simulation results.