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This paper provides an overview of the power, packaging, and cooling aspects of the IBM eServer z900 design. The semiconductor processor chips must be supported and protected in a mechanical structure that has to provide electrical interconnects while maintaining the chip junction temperature within specified limits. The mechanical structure should be able to withstand shock and vibrations during transportation or events such as earthquakes. The processor chips require electrical power at well-regulated voltages, unaffected by the ac-line voltage and load current fluctuations. The acoustical and electromagnetic noise produced by the hardware must be within the limits set by national regulatory agencies, and the electronic operations must be adequately protected from disruption caused by electromagnetic radiation. For high availability, the power, packaging, and cooling hardware must have redundancy and the ability to be maintained while the system is operating. This paper first overviews the packaging hardware, followed by a description of the firstand second-level packaging, which includes the mother board and the multichip module. Thermal management is discussed from the point of view of both the multichip module and the overall system. Power conversion, management, and distribution are presented next. Finally, the design aspects involved with meeting the requirements of electromagnetic compatibility, acoustics, and immunity to shock, vibration, and earthquakes are discussed.