The paper describes development, realization and verification of more precise analytical models for the study of the basic performance parameters of parallel computers based on connected parallel computers (Cluster, NOW, Grid). At first the paper describes very shortly the developing steps of parallel computer architecture and then he summarized the basic concepts for performance modeling of mentioned parallel computers. To illustrate theoretical evaluation concepts the paper considers in its

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... perimental part the achieved results on concrete analyzed examples and their comparison. The suggested model considers for every node of the NOW or Grid networks one part for the own workstation's activities and another one for node's communication channel modeling of performed data communications. In case of using multiprocessor system, as modern node's communication processor, the suggested model considers for own node's activities M/D/m queuing theory system and for every node's communication channel M/D/1 system. Based on these more realistic assumptions we have been developed improved analytical models to account the real no exponential nature of the inputs to the modeling queuing systems. The achieved results of the developed models were compared with the results of the common used analytical and simulation model to estimate the magnitude of their improvement. The developed analytical models could be used under various ranges of input analytical parameters, which influence the architecture of NOW or Grid computer networks and which are interested from the sight of practical using. These consequences are in relation to the developed analytical models and their verifications through simulation model.