The WIMP51: A Simple Processor and Visualization Tool to Introduce Undergraduates to Computer Organization

Abstract

The University of Missouri – Rolla offers a Junior-level lecture and laboratory course in hardware/software co-design 1 .  The course focuses on the 8051 family of microcontrollers.  Many students who take this course have no prior experience with processor architecture, so a short introduction to some basic concepts of computer organization is given in the first few weeks of the course. In the past, the computer architecture portion of the course was taught using the Gnome processor, described in Van den Bout’s Practical Xilinx Designers Lab Book 2 .  The Gnome is a four-bit processor with eightbit instructions described in VHDL and targeted for the Xilinx 4k series FPGA.  While the Gnome is at an appropriate level of complexity for the course, it is quite different from the 8051 microcontroller.  Past course evaluations indicate that many students feel their time was wasted learning the Gnome instruction set, only to be told to forget the Gnome instructions and learn a new instruction set three weeks into the course.  Still, the Gnome is useful in the classroom, as the 8051 microcontroller is much too complex for a short introduction to computer architecture. To resolve these problems a replacement processor  based  on  the  8051  was designed. Called  the  WIMP51,  it  is  a  simple binary- compatible subset of the 8051, lacking internal memory, interrupts, peripherals, and many of the 8051 instructions.  The WIMP51 was implemented in synthesizable VHDL and an interactive graphical simulator was developed for use in lab.