Minimal Instruction Set Computers

The term MISC refers to Minimal Instruction Set Computers in general, and to the chips designed by Chuck Moore at Computer Cowboys. These chips are unusual in many ways. They are designed on Chuck's VLSI CAD software called OKAD. They are implemented in CMOS Silicon VLSI processes and are very small and fast. They use a CPU architecture based on the Forth computer language, and with only five bit instructions. The first chip to be produced at Computer Cowboys was MuP21. MuP21 stands for Multi-Micro Processor. With only 25 instructions MuP21 is a Minimal Instruction Set Computer. But it is not just he instruction set that has been minimized, much of the complexity in modern chips is gone. MuP21 is implemented in only 7000 transistors vs millions of transistors on other modern chips. MuP21 includes not only a Forth Engine CPU, but also a memory interface processor, and a video output processor on the chip. With only 7000 CMOS transistors MuP21 can execute 80 million instructions per second and only draw 50 milliwatts of power.

A paper entitled MuP21 a High Performance MISC Processor was published by Charles Moore and C.H. Ting in the January 1995 issue of Forth Dimensions.

Ultra Technology Inc. is developing the F21 Microprocessor

MISC Mail List

FOr a number of years we had a mail list setup at for a discussion of various aspects of the MISC approach -- Minimal Instruction Set Chips. The first MISC chip is out and can be ordered from Offete Enterprises Inc. -- MuP21. Ultra Technology Inc. is completing the F21 Microprocessor

We have three new (3/15/2001) mail lists for related discusions:

MachineForth, ColorForth, and Nosc

MachineForth is the native assembler for MISC chips and colorForth is about Chuck Moore and other people's versions of Color Forth. Chuck's new OKAD II was written in his new Color Forth. Nosc is for discussions of No Operand Set Computer or Minimal Instruction set computers.

To subscribe to the above mail lists send mail to: or or or

No subject or boday is needed. Then reply to the confirmation mail sent to you by the list without changing it. The mail lists do have a web browsable archive. web browsable archive.

A free simulator for the MuP21 called S21 is available at this site. And more complex free simulators and emulators for UltraTechnology's F21 microprocessor.
Jeff Fox
UltraTecnology Homepage