CSE $332$: Computer Organization and Architecture

Instructor: Dr$.$ Mohammad Abdul Qayum $($MAQm$)$

Office: SAC $1044$ A

E$-$mail : mohammad.qayum@northsouth.edu

Phone: $02-55668200$ Ext. $6186$

Design Your Own CPU & Assembler

One of the course objectives is to be able to design a complete CPU system. It starts with

learning about ISA, advanced ALU, data path and control, pipelining in theory. In order to make

this learning more effective a step by design of the complete CPU system is carried out through

pen and paper, simulation tools, hardware etc. Students work in a group and try to develop small

pieces and finally connect them together to get their cpu as explained in the following diagram.

Title : ISA Design Type: Document

Consider yourself as a computer architect and you are employed in a vendor company. The

company told you that they are going to design a new $32$ bit single$-$cycle CPU that has separate

Data and Instruction Memory. The ISA should be general purpose enough to be able to run

provided general programs

Input$/$Output Operations

It should also be able to connect with the display unit $($ex: seven segment display$)$ to display

results or any data and a keyboard or something similar to get input from the user. you should

make any necessary arrangements $($ extra instruction or special register or any other $)$ to

accommodate this external communication into your ISA design. For example, you might

consider including dedicated instructions like IN & OUT to perform the input$/$output operations.

Design requirements

As an ISA designer your job is to propose a detailed design of the ISA. Few of the issues

probably you would have to address are given below:

$1)$ How many operands?

$2)$ Types of operand? $($Register based?? Memory$-$based? Mixed?$)$

$3)$ How many operations? Why $?$

$4)$ Types of operations? $($Arithmetic$,$logical$,$branch type?? How many from each category? Draw

a table with list of instructions, instruction type, their opcode, functionality $($if any$)$

$5)$ How many formats would you choose? Draw the formats along with field name and number of

bits in each field

$6)$ list of registers? Draw a register table. $($with register name and values$)$

Benchmark Programs

You have to design your ISA focusing on the following three categories of programs

a$)$ Simple arithmetic & logic operations

b$)$ Programs that requires checking conditions

c$)$ Loop type of program s

Guideline

Your assignment will be evaluated according to the following criteria:

$1.$ Ability to execute the provided benchmark programs $($test programs$),$ and other general

purpose programs?

$2.$ How much is it different from existing ISAs such as MIPS?

$3.$ If it is very similar to MIPS, provide your reasonings behind the outcome.

You must answer those with your reasoning. While you are deciding on the above issues, you

might consider some sample high level program that can be run on this CPU using your ISA.

Say, during the decisions about the types of operation to include, you can think about the type of

high$-$level language program it will be able to execute. Design might vary from one group to

another and there might be multiple possible solutions. You will be scored based on your clear

reasoning.

Title : Assembler Type : Software

It is difficult and error$-$prone to manually write machine code. The problem can be addressed by

writing an assembler, which can automatically generate a machine code from an assembly file. In

this project, you will use an assembler for your ISA. The assembler reads a program written

using assembly language in a text file $(.$asm or $.$s$),$ then translates it into binary code and

generates an output file $(.$txt or $.$bin$)$ containing machine code. The generated output files will

later be useful to run a program when you will develop your actual CPU in verilog. Language:

You can use any high$-$level language. Some demo codes are provided in the following link $($the

model output is binary that includes address, you may need to remove it along with any spaces

between binaries$).$ You are strongly advised to use the example to save your time. You might

need to modify the existing functions$/$classes to fit your needs.

Also, you can take advantage of AI such as ChatGPT or Bard to develop your own assembler.

I$/$O fromat:

The input code will be written in a text file $($e$.$g$.$ extension bin$)$ in assembly format following

your ISA. There will be one instruction per line. The output will be generated