IBM POWER

IBM POWER. The IBM POWER architecture is a family of RISC-based instruction set architectures designed by IBM for high-performance computing. First introduced in the early 1990s, it has powered a wide range of systems from workstations to the world's most powerful supercomputers. The architecture is known for its scalability, robust multiprocessing capabilities, and a strong focus on reliability, availability and serviceability.

History

The lineage of the architecture traces back to the pioneering IBM 801 research project led by John Cocke in the 1970s, which established key RISC concepts. This work directly influenced the development of the IBM ROMP processor used in the IBM RT PC. In the late 1980s, a new project within IBM codenamed "America Project" aimed to create a high-performance RISC architecture for a new line of workstations. This effort culminated in the announcement of the first POWER1-based systems, the IBM RISC System/6000 family, in 1990. A pivotal moment came in 1991 with the formation of the AIM alliance between IBM, Apple Inc., and Motorola, which led to the creation of the derived PowerPC architecture for the Apple Macintosh and other markets. Subsequent generations, including the influential POWER4 which introduced simultaneous multithreading and the first mainstream multicore processor, solidified its role in enterprise servers and supercomputing, most notably within the IBM Deep Blue and IBM Watson systems.

Architecture

The architecture is a classic load-store RISC design emphasizing simplicity and high instruction throughput. A defining feature is its use of a large, unified set of general-purpose registers and separate floating-point registers, facilitating complex numerical computations. It employs a robust superscalar execution model, allowing multiple instructions to be issued and completed per clock cycle. Key architectural innovations include advanced branch prediction units, extensive out-of-order execution capabilities, and sophisticated memory management unit designs supporting very large virtual memory address spaces. The architecture has also incorporated specialized extensions like AltiVec for SIMD operations, crucial for scientific and multimedia workloads. Its design strongly emphasizes symmetric multiprocessing and non-uniform memory access configurations, making it highly scalable in large server and cluster computing environments.

Processor models

The implementation of the architecture has evolved through multiple distinct processor families. The initial POWER1 processors, such as those in the IBM RISC System/6000, integrated floating-point units on-chip. The POWER2 added a second fixed-point unit and enhanced cache. The transition to PowerPC for desktops saw chips like the PowerPC 601 and PowerPC G5. For enterprise systems, the POWER3 brought full 64-bit support, while the groundbreaking POWER4 was the first commercially available multicore processor. The POWER5 introduced simultaneous multithreading and an on-chip memory controller, and the POWER6 focused on very high clock speeds and decimal floating-point arithmetic. The POWER7 increased core counts and added enhanced threading, and the POWER8 introduced support for CAPI and open acceleration. The POWER9 is foundational to major systems like the Summit (supercomputer) and Sierra (supercomputer), and the latest POWER10 further advances performance per watt and security features.

Operating system support

A variety of operating systems have been ported to run on hardware. The primary historically was IBM AIX, IBM's proprietary Unix system, which has been optimized across every generation. Another significant Unix variant was IBM i, originally known as OS/400, for the IBM AS/400 and later Power Systems servers. The architecture also gained support for the Linux kernel starting in the late 1990s, leading to major distributions like Red Hat Enterprise Linux and SUSE Linux Enterprise Server offering robust support. While the Mac OS ran on PowerPC derivatives, modern support for the mainline servers is dominated by AIX, IBM i, and Linux. The OpenPOWER Foundation has further encouraged development of Linux and other open-source software for the ecosystem.

See also

* PowerPC * OpenPOWER Foundation * IBM Power Systems * Supercomputer * RISC-V Category:Instruction set architectures Category:IBM microprocessors Category:RISC architectures