Abstract.For some time, the method of Ramaswami has been the established way to analyze M/G/1-type processes. The ETAQA method, proposed previously in [15], has offered a more efficient alternative for the exact computation of a general class of metrics for M/G/1-type processes. However, the stability of ETAQA and its relation to Ramaswami's method were not well understood. In this paper, we derive a new formulation that improves the numerical stability and computational performance of ETAQA. As with ETAQA, the resulting methodology, newETAQA, solves a homogeneous system of equations to obtain the aggregate probability of a finite set of classes of states from the state space. In contrast to ETAQA, newETAQA constructs its matrix X in a way similar to the method of Ramaswami, decoupling the computation of the probabilities of the first two initial classes of states from the computation of the aggregate probability. Because direct methods are used to solve this system, the decoupling implies an often significant speedup over ETAQA. In addition, we show that the matrix X is an M-matrix, and under certain conditions, X is also diagonally dominant and thus can be factored stably. More importantly, we show that the newETAQA method is just an efficient way to implement Ramaswami's method. We also discuss alternative normalization conditions for Ramaswami's method. Our numerical experiments demonstrate the stability of our method for both stiff and well behaved processes, and for both low and high system utilizations.