Instruction Set Architectures (1)

Question 1

What are the different types of MIPS registers and their purposes?

Answer 1

General-purpose registers include temporary ($t), saved ($s), argument ($a), return address ($ra), global pointer ($gp), stack pointer ($sp), and frame pointer ($fp)

Question 2

What is the purpose of the Arithmetic and Logic Unit (ALU) in the Processing Unit?

Answer 2

It performs arithmetic and logical operations on data

Question 3

What are the fundamental components of the von Neumann model?

Answer 3

• Memory
• Processing Unit
• Input
• Output
• Control Unit

Question 4

How is an addition operation represented in MIPS assembly language?

Answer 4

Using the ‘add’ instruction: add $d, $s, $t, where $d is the destination and $s, $t are source operands

Question 5

How does the MIPS assembly handle the loading of immediate values?

Answer 5

Using the ‘li’ (load immediate) instruction, or through a combination of ‘lui’ (load upper immediate) and ‘ori’ (OR immediate)

Question 6

What key functions does the Control Unit perform in a computer system?

Answer 6

It directs the operation of the processor and coordinates the activities of the other components

Question 7

How does MIPS handle temporary variables during function calls?

Answer 7

Temporary variables can be stored in $t registers, which are not preserved across function calls

Question 8

How do data movement instructions in MIPS function?

Answer 8

They read data from memory or write data to memory

Question 9

What role do immediate values play in MIPS instructions?

Answer 9

Immediate values provide constants directly in the instruction for operations without requiring a separate load

Question 10

What are the conventions surrounding caller and callee functions in MIPS?

Answer 10

The caller passes arguments and jumps to the callee, which must return the result without overwriting essential registers

Question 11

What is the major difference between RISC and CISC architectures?

Answer 11

RISC (Reduced Instruction Set Computer) uses a small, highly optimised instruction set, while CISC (Complex Instruction Set Computer) uses a larger set of instructions, including more complex ones

Question 12

What is the significance of the ‘shamt’ field in the R-format instruction?

Answer 12

The ‘shamt’ field specifies the amount of shift for shift operations in R-format instructions

Question 13

How many types of instructions are defined in the MIPS ISA?

Answer 13

Three main types: Operate instructions, Data movement instructions, and Control flow instructions

Question 14

How is a MIPS function call executed with the jump and link (jal) instruction?

Answer 14

‘jal’ saves the return address in $ra and jumps to the specified function

Question 15

What is meant by ‘word length’ in the context of the MIPS architecture?

Answer 15

In MIPS, word length is 32 bits, meaning integers and addresses are typically 32 bits long

Question 16

How does an Instruction Set Architecture (ISA) differ from microarchitecture?

Answer 16

ISA defines the set of instructions a processor can execute, while microarchitecture refers to how those instructions are implemented in hardware

Question 17

How is the instruction format structured in MIPS?

Answer 17

There are multiple formats: R-format, I-format, and J-format, each with specific fields and layouts for different types of instructions

Question 18

Why is the concept of modular functions important in programming?

Answer 18

Modular functions enhance code reusability, readability, and maintainability by encapsulating functionality

Question 19

How are conditional branches implemented in MIPS assembly code?

Answer 19

Using instructions like ‘beq’ for branching based on equality or ‘bne’ for branching based on inequality

Question 20

How are arrays accessed in MIPS assembly programming?

Answer 20

By loading the base address into a register and using offsets to access elements

Question 21

In MIPS, how is a while loop structure typically represented in assembly?

Answer 21

Using a combination of branch instructions to check the loop condition and jump back to the start of the loop

Question 22

What is the difference between load word (lw) and store word (sw) instructions?

Answer 22

‘lw’ retrieves a word from memory into a register, while ‘sw’ stores a word from a register into memory

Question 23

What happens during a procedure return in MIPS assembly language?

Answer 23

The return address is retrieved from $ra, and control is transferred back to the caller using ‘jr $ra’

Question 24

What is the role of the stack pointer in MIPS architecture?

Answer 24

The stack pointer ($sp) points to the top of the current stack frame, managing local variables and function arguments

Question 25

How does the R-format instruction in MIPS differ from I-format instruction?

Answer 25

R-format instructions use three registers; I-format includes an immediate value

Question 26

What instruction is used to implement a branch instruction in MIPS?

Answer 26

Branch instructions like ‘beq’ (branch if equal) and ‘bne’ (branch if not equal) are used

Question 27

What are the steps involved in a for loop implementation in MIPS?

Answer 27

Initialize the loop variable, check the condition with a branch, perform body actions, increment the loop variable, and loop back

Question 28

How does MIPS handle function return values?

Answer 28

Return values are typically stored in the $v0 register by the callee and accessed by the caller after a return

Question 29

What is the significance of the PC or IP in the von Neumann architecture?

Answer 29

PC (Program Counter) or IP (Instruction Pointer) tracks the address of the next instruction to be executed

Question 30

How are MIPS instructions encoded in terms of binary representation?

Answer 30

MIPS instructions are encoded as 32-bit instruction words called machine code