This paper describes architectures and significant implementation features of two systems in the IBM POWER8™ processor-based family of servers. Specifically, the scale-out 2-socket rack server and the enterprise scale-up 16-socket rack server are detailed. The description of these systems highlights the increase in memory bandwidth from previous POWER® systems, the enablement of coherent accelerators, the highly-extensible I/O subsystem, and the high-performance directly attached storage subsystem. In addition, reliability, availability, and serviceability features are described. These systems deliver significant increases in core count, memory, and input/output bandwidth over previous POWER systems - with reliability and availability enhancements commensurate with the performance improvements.