1. Computer Architecture & Operations I
Instructor: Ryan Florin

2. Representing Instructions
The University of Adelaide, School of Computer Science
21 September 2018
Representing Instructions
Instructions are encoded in binary
Called machine code
MIPS instructions
Encoded as 32-bit instruction words
Small number of formats encoding operation code (opcode), register numbers, …
Regularity!
Register numbers
$t0 – $t7 are reg’s 8 – 15
$t8 – $t9 are reg’s 24 – 25
$s0 – $s7 are reg’s 16 – 23
§2.5 Representing Instructions in the Computer
Chapter 2 — Instructions: Language of the Computer

3. The University of Adelaide, School of Computer Science
21 September 2018
Mini Green Sheet
MIPS instructions R: I:
Register numbers
$t0 – $t7 : 8 – 15, $t8 – $t9 : 24 – 25
$s0 – $s7 : 16 – 23, $zero : 0 op rs rt rd
shamt
funct
6 bits
5 bits op rs rt
constant or address
6 bits
5 bits
16 bits
Chapter 2 — Instructions: Language of the Computer

4. What does this do? add $s1 $zero $zero lw $s0 4($s2) add $s1 $s1 $s0
sw $s1 0($s2)

5. Practice Write the following in MIPS $t0 = $t1 + 48
$s0 = $t1 + $t2 + $t3
$s0 = ($t1 + $t2) * 16

6. Convert into MIPS Are these R type or I type? 2231 0080 8e50 0008 ae

7. The University of Adelaide, School of Computer Science
21 September 2018
Convert into MIPS
MIPS instructions R: I:
How to tell the difference between R type and I type? Look at the Green sheet to spot the difference. op rs rt rd
shamt
funct
6 bits
5 bits op rs rt
constant or address
6 bits
5 bits
16 bits
Chapter 2 — Instructions: Language of the Computer

8. What to do
Review Chapter 2
Start the homework!