An overview of the IBM zEnterprise EC12 processor cooling system

On September 19, 2012 IBM announced its latest System z Enterprise Class zServer, the IBM zEnterprise EC12 (zEC12). This server uses a 96 mm glass ceramic substrate to interconnect processors and related cache chips on a multi-chip module (MCM). In rare applications, the power in these MCMs can exceed 2000W, well beyond air cooling capability. This paper describes a new cooling methodology IBM employs in zEC12 to cool its processor MCMs. From the IBM S/390 G4, which first shipped in 1997, through z196 which is EC12's enterprise class predecessor, IBM's high end System z servers have utilized vapor compression refrigeration to cool its processor MCMs. In zEC12, the thermal solution employs an air to water heat exchanger to provide this function. This paper discusses the technical details of this cooling system. Thermal performance of each component of the cooling path from processor core to ambient, as well as comparison to prior cooling approaches in terms of temperatures, reliability, and energy efficiency will be reviewed. In summary, this technology shows considerable promise for cooling this class of server.