Waiting time calculations for K machines with 2 service facilities

Abstract Traditional multi-channel queueing models assume that if you have 2 service facilities serving K machines, that the service characteristics of both facilities are identical. Suppose that the service facilities are quite different, though; e.g. electrical vs. mechanical, or hardware vs. software, or 2 different types of computers. This paper shows that when the 2 service facilities are distinctly different, the waiting times are always greater than or equal to the case where the service characteristics are the same. The paper 1. a) presents formulas for the waiting times for 2 distinct servers, and 2. b) compares the results to the (lower bound) waiting times for 2 identical servers.