Joachim Gerhard Clabes

The circuit and physical design of the POWER4 microprocessor

The IBM POWER4 processor is a 174-milliontransistor chip that runs at a clock frequency of greater than 1.3 GHz. It contains two microprocessor cores, high-speed buses, and an on-chip memory subsystem. The complexity and size of POWER4, together with its high operating frequency, presented a number of significant challenges for its multisite design team. This paper describes the circuit and physical design of POWER4 and gives results that were achieved. Emphasis is placed on aspects of the design methodology, clock distribution, circuits, power, integration, and timing that enabled the design team to meet the project goals and to complete the design on schedule.

Design and implementation of the POWER5/spl trade/ microprocessor

POWER5/sup TM/ is the next generation of IBMs POWER microprocessors. This design, sets a new standard of server performance by incorporating simultaneous multithreading (SMT), an enhanced distributed switch and memory subsystem supporting 164w SMP, and extensive RAS support. First pass hardware using IBMs 130nm silicon-on-insulator technology operates above 1.5GHz at 1.3V. POWER5s dual-threaded SMT creates up to two virtual processors per core, improving execution unit utilization and masking memory latency. Although a simplistic SMT implementation promised /spl sim/20% performance improvement, resizing critical microarchitectural resources almost doubles in many cases the SMT performance benefit at a 24% area. Implementing these microarchitectural enhancements posed challenges in meeting the chips frequency, area, power, and thermal targets.