IBM 801

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IBM 801

The 801 was a RISC CPU

Central processing unit

A central processing unit is an electronic circuit that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage....
designed by IBM in the 1970s, and used in various roles in IBM until the 1980s.

The 801 started as a pure research project led by John Cocke

John Cocke

John Cocke was an American computer scientist recognised for his large contribution to computer architecture and optimizing compiler design. He is considered by many to be "the father of RISC architecture."...
at the Thomas J. Watson Research Center

Thomas J. Watson Research Center

The Thomas J. Watson Research Center is the headquarters for the IBM Research Division.The center is on three sites, with the main laboratory in Yorktown Heights, New York, 38 miles north of New York City, a building in Hawthorne, New York, and offices in Cambridge, Massachusetts....
in building 801. They were looking for ways to improve performance of their existing machines, studying traces of programs running on System/370

System/370

The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the product announcement....
mainframes and looking at the compiler code. From this project led the idea that it was possible to make a very small and very fast core, which could then be used to implement the microcode

Microcode

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Encyclopedia

The 801 was a RISC CPU

Central processing unit

John Cocke

Thomas J. Watson Research Center

System/370

Microcode

Microcode is a layer of lowest-level instructions involved in the implementation of machine code instructions in many computers and other processors; it resides in a special high-speed memory and translates machine instructions into sequences of detailed circuit-level operations....
for any machine.

The project then moved on to produce the design as a CPU, also called the 801. The resulting CPU was operational by the summer of 1980 and was implemented using Motorola MECL-10K technology on large wire wrapped custom boards. The CPU was clocked at 66 ns cycles (approximately 15.15 MHz) and could compute at the then-fast speed of approximately 15 MIPS. This prototype design was a 24-bit implementation without virtual memory

Virtual memory

Virtual memory is a computer system technique which gives an application program the impression that it has contiguous working memory , while in fact it may be physically fragmented and may even overflow on to disk storage....
. The 801 architecture was used in a variety of IBM devices including channel controllers for their 370 mainframes, various networking devices, and eventually the IBM 9370 mainframe core itself.

In the early 1980s the lessons learned on the 801 were put back into the new America Project, which led to the IBM POWER

IBM POWER

POWER is a RISC instruction set architecture designed by International Business Machines. The name is a backronym for Performance Optimization With Enhanced RISC....
architecture and the RS/6000

RS/6000

RISC System/6000, or RS/6000 for short, is a family of RISC and UNIX based Server s, workstations and supercomputers made by IBM in the 1990s....
deskside scientific microcomputer.

John Cocke

John Cocke

Turing Award

The A. M. Turing Award is given annually by the Association for Computing Machinery to "an individual selected for contributions of a technical nature made to the computing community....
and the Presidential Medal of Science for his work on the 801.

External links

– IBM Journal of R&D, Volume 44, Numbers 1/2, p.48 (2000)