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IBM POWER microprocessors


IBM has a series of high performance microprocessors called POWER followed by a number designating generation, i.e. POWER1, POWER2, POWER3 and so forth up to the latest POWER9. These processor have been used by IBM in their RS/6000, AS/400, pSeries, iSeries, System p, System i and Power Systems line of servers and supercomputers. They have also been used in data storage devices by IBM and by other server manufacturers like Bull and Hitachi.

The POWERn family of processors were developed in the late 1980s and are still in active development nearly 30 years later. In the beginning, they utilized the POWER instruction set architecture (ISA), but that evolved into PowerPC in later generations and then to Power Architecture. Today, only the naming scheme remains the same; modern POWER processors do not use the POWER ISA.

In 1974 IBM started a project to build a telephone switching computer with, for the time, immense computational power. Since the application was comparably simple, this machine would need only to perform I/O, branches, add register-register, move data between registers and memory, and would have no need for special instructions to perform heavy arithmetic. This simple design philosophy, whereby each step of a complex operation is specified explicitly by one machine instruction, and all instructions are required to complete in the same constant time, would later come to be known as RISC. When the telephone switch project was cancelled IBM kept the design for the general purpose processor and named it 801 after building #801 at Thomas J. Watson Research Center.


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