Packaging the IBM eServer z990 central electronic complex

The z990 eServer central electronic complex (CEC) houses four multichip-module-based processor units instead of one, as in the previous-generation z900 eServer. The multichip module (MCM) input/output pin density in z990 processor units is more than twice that of the MCMs in z900 processor units. This increase in packaging density and the consequent tripling of the current drawn by the processor units were accommodated by the first-time use of land grid array (LGA) MCM-to-board interconnections in an IBM zSeries eServer. This was done by using innovative refrigeration cooling of the MCM with air cooling as backup, and by a new mechanical packaging and power distribution scheme. This paper describes the mechanical engineering of the CEC cage, the LGA MCMto-board interconnection scheme, and the mechanical isolation of the MCM evaporator– heat-sink mass from the LGA contacts. The paper also describes the electrical power and the cooling solutions implemented to meet the more demanding requirements of the denser CEC package.