1. ACOE301: Computer Architecture II Labs

2. Lab conduct Time: 1 period/week Location: Room 12
Material: MIPS Assembly
Equipment: SPIM MIPS emulator, PC
Deliverables: Lab papers with source code and answers to questions
Deliverable submission mode: e-learning page

3. SPIM a self-contained simulator that runs MIPS32 programs
reads and executes assembly language programs
provides a simple debugger and minimal set of operating system services
does not execute binary (compiled) programs.
Latest version is QTSPIM

5. Advantages of using a Simulator
You can learn the language without having to buy a MIPS-based computer
The simulator provides debugging features
single stepping through a Program
watch the contents of the registers change as each instruction executes
look at the contents of memory as the instructions execute
set breakpoints
programming mistakes do not cause the machine running the simulation to crash
Disadvantage: Slow

6. Assembly language
One-to-one relationship with machine language unlike high-level languages
Many lines of code even for simple programmes
Requires at least some knowledge of the microprocessor architecture, memory structure and operating system
Not portable (source files will not run on a different architecture microprocessor)

7. Why use Assembly Language
Traditionally, more efficient use of the main memory
Less memory required
Programs execute faster
Traditionally, avoid redundant instructions inserted by compilers.
Direct access to the hardware of the computer,
Usually not supported or even prevented by compilers.
Access to the microprocessor’s internal control registers.
Embedded systems have tight constraints on performance, memory size and power consumption

8. Additional Reasons for Learning Assembly Language
Understand the microprocessor architecture
Understand the hardware/software interface

9. Typical Assembly Language Instruction
LOOP: add $3, $3, $2 ;$3<-$3+$2
Label (optional)
Opcode
Destination operand
Source operand(s)
Comment (optional)

10. Assembler Directives
Directives are instructions given by the programmer to the assembler on how to assemble the program.
Directives are not part of the instruction set of the microprocessor.
The use of directives might vary from assembler to assembler.
Some MIPS assembler directives:
.data declares a data memory segment where you can declare ‘variables’
.text declares a code memory segment where a program is stored
.word declares word size (32-bit) variables or constants
.byte declares byte size (8-bit) variables or constants
.ascii declares a non null-terminated ascii string
.asciiz declares a null-terminated ascii string