The IBM system z10 includes four microprocessor cores - each with a private 3-Mbyte cache - and integrated accelerators for decimal floating-point computation, cryptography, and data compression. A separate SMP hub chip provides a shared third-level cache and interconnect fabric for multiprocessor scaling. This article focuses on the high-frequency design techniques used to achieve a 4.4-GHz system, and on the pipeline design that optimizes z10's CPU performance.