IBM 801

The 801 was a RISC CPU 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 at the Thomas J. Watson Research Center in building 801. They were looking for ways to improve performance of their existing machines, studying traces of programs running on System/370 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 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. 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 architecture and the RS/6000 deskside scientific microcomputer.

John Cocke later won both the Turing award and the Presidential Medal of Science for his work on the 801.

External links

• The evolution of RISC technology at IBM by John Cocke – IBM Journal of R&D, Volume 44, Numbers 1/2, p.48 (2000)