A power packaging and cooling overview of the IBM eServer z900 by P Singh S J Ahladas W D Becker F E Bosco J P Corrado G F Goth S Iruvanti M A Nobile B D Notohardjono J H Quick E J Seminaro K M Soohoo C Wu 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 first and 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 Introduction The disciplines of power packaging and cooling are essential to the design and manufacture of a commercial computer The conversion of semiconductor processing chips into functioning components requires packaging of the chips placing the packaged chips on circuit boards with the appropriate electrical interconnections delivering well regulated electrical power to the processor chips removing the heat generated by the chips and providing mechanical hardware to support this infrastructure These Copyright 2002 by International Business Machines Corporation Copying in printed form for private use is permitted without payment of royalty provided that 1 each reproduction is done without alteration and 2 the Journal reference and IBM copyright notice are included on the first page The title and abstract but no other portions of this paper may be copied or distributed royalty free without further permission by computer based and other information service systems Permission to republish any other portion of this paper must be obtained from the Editor 0018 8646 02 5 00 2002 IBM IBM J RES DEV VOL 46 NO 6 NOVEMBER 2002 P SINGH ET AL 711 BPAs BPA MRU MRU BPA MRUs CEC cage midplane CEC cage I O cage a I O cage midplane b Figure 1 a Front view and b side view of a z900 server showing the four subsystem building blocks bulk power assemblies BPAs modular refrigeration units MRUs central electronic complex CEC cage and input output I O cage tasks are essential to creating a computer that has high reliability essentially zero downtime minimal floor space and power requirements the ability to be powered by a wide range of ac or dc line voltages no objectionable electromagnetic radiation or acoustical noise and the ability to withstand electromagnetic radiation mechanical shock and vibration within specified limits While a truly extraordinary product is one that employs state of the art components it also requires a premier packaging power and cooling design Using the IBM eServer z900 as an example the aim of this paper is to describe the following portions of the development of a computing system the electronic package the power conversion and delivery subsystem the cooling subsystem and the mechanical support infrastructure System package overview The IBM eServer z900 comprises four subsystem building blocks packaged in a steel frame as shown in Figure 1 The four subsystems are the bulk power assembly BPA the central electronic complex CEC cage the input output I O cage and the modular refrigeration unit MRU They are powered and controlled through a network of cables called universal power input cables 1 UPICs and a service control Ethernet based network of hardware and software referred to as the power service 712 1 A UPIC cable connects a power distribution unit to a DCA or a motor drive and contains both the branch circuit power feed and the communications link P SINGH ET AL 2 control network PSCM The system architecture supports both single and dual frame configurations depending on the number of I O cages included The single frame configuration consists of a frame referred to as the A frame while the dual frame configuration adds an expansion frame referred to as the Z frame to house additional I O cages In a dual frame configuration power to the complete system is usually provided by two BPAs in the top section of the A frame However when system power requirements exceed the power available from the two BPAs in the A frame the dual frame system is reconfigured such that the top section of the A frame and its BPA contents are eliminated and power to the complete system is supplied by two larger BPAs installed in the space above the I O cages in the Z frame The front and rear views of a two frame system are shown in Figure 2 The system enclosure provides roughly 10 dB of acoustical noise attenuation primarily through the use of specially designed front and rear acoustical doors The enclosure is also designed to meet FCC regulations and limits for electromagnetic compatibility EMC and the containment of electromagnetic interference EMI The system requires n 1 redundancy across all subsystems where n is the number of subsystems needed for operation of the system A failed subsystem is fieldreplaceable or repairable during concurrent operation of the system This requirement necessitates the use of two BPA subsystems which are mirrored about the midplane of the server Each can independently power the entire server There are two BPA subsystem designs one with up to 13 kW and the other with up to 19 5 kW of power delivery capability Dual redundant line cords bring in 200 480 Vac power which is converted to 350 Vdc by the BPAs and distributed to point of load dc dc converters and motor drives The point of load dc dc converters are housed
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