IMPROVING THE SCALABILITY OF HIGH PERFORMANCE COMPUTER SYSTEMSInauguraldissertationzur Erlangung des akademischen Gradeseines Doktors der Naturwissenschaftender Universität Mannheimvorgelegt vonHeiner Hannes Litzaus Heidelberg(Diplom-Informatiker der Technischen Informatik)Mannheim, 2010Dekan: Professor Dr. W. Effelsberg, Universität MannheimReferent:. U. Brüning, Universität HeidelbergKorreferent: Professor Dr. R. Männer, Universität HeidelbergTag der mündlichen Prüfung: 17. März 2011Für RegineAbstractImproving the performance of future computing systems will be based upon the abilityof increasing the scalability of current technology. New paths need to be explored, asoperating principles that were applied up to now are becoming irrelevant for upcomingcomputer architectures. It appears that scaling the number of cores, processors and nodeswithin an system represents the only feasible alternative to achieve Exascale performance.To accomplish this goal, we propose three novel techniques addressing different layers ofcomputer systems. The Tightly Coupled Cluster technique significantly improves thecommunication for inter node communication within compute clusters. By improving thelatency by an order of magnitude over existing solutions the cost of communication isconsiderably reduced. This enables to exploit fine grain parallelism within applications,thereby, extending the scalability considerably.