Harris RTX 2000

The Harris Semiconductor RTX 2000, now manufactured by Intersil, is a 16-bit stack machine microprocessor architecture designed for real-time computing and programmed primarily in Forth.

An updated version, the NC5016, ran at 10 MHz and 12 MIPS, and a planned NC6016 appears to not entered production and Novix shut down during this period.

A stack machine contrasts with traditional designs in that it lacks general purpose processor registers defined in the instruction set architecture.

Instead it uses addressing modes based on offsets in the stack, which is normally stored in main memory or partially cached in registers that are not visible to the programmer.

[1] It also has a very low and consistent interrupt latency of only four processor cycles, which lends it well to realtime applications.

The chip could directly execute 40 Forth primitives and 123 combinations, eliminating the need for a complete virtual machine and speeding performance of the most common instructions.

[1] In 1988, Harris Semiconductor purchased the rights to the Novix line and began an improvement program.