Week 4 - Instruction Set Architecture (Part 2)

Question 1

What are the primary components of the Von Neumann model?

Answer 1

The primary components of the Von Neumann model are:

Memory
Processing Unit (ALU)
Control Unit
Input
Output

Question 2

What is the function of the Control Unit in the Von Neumann model?

Answer 2

The Control Unit directs the execution of instructions by fetching, decoding, and executing them. It controls the flow of data between the CPU, memory, and input/output devices.

Question 3

What is the Instruction Cycle in the Von Neumann architecture?

Answer 3

The instruction cycle consists of three main steps:

Fetch: Retrieve the instruction from memory.
Decode: Interpret the instruction.
Execute: Perform the action specified by the instruction.

Question 4

What is stacking in computer architecture, and why is it used?

Answer 4

Stacking refers to using a stack (LIFO structure) to store temporary data such as function parameters, local variables, and return addresses during function calls. It is used to manage data efficiently during recursive calls and nested functions.

Question 5

What is addressability in memory systems?

Answer 5

Addressability refers to the number of bits accessed in a single memory operation. For example, systems can be byte-addressable (accessing 8 bits) or word-addressable (accessing multiple bytes in one operation).

Question 6

What is the address space in memory?

Answer 6

The address space is the total number of uniquely addressable memory locations in a system. For example, a 16-bit address space allows for
2¹⁶ or 65,536 unique addresses.

Question 7

How does byte-addressable memory differ from word-addressable memory?

Answer 7

In byte-addressable memory, each byte has a unique address. In word-addressable memory, each word (a group of bytes) has a unique address, and the word size can vary (e.g., 16-bit, 32-bit, or 64-bit).

Question 8

What is the difference between Big Endian and Little Endian memory storage?

Answer 8

Big Endian: The most significant byte (MSB) is stored at the lowest memory address.
Little Endian: The least significant byte (LSB) is stored at the lowest memory address.

Question 9

What are the Memory Address Register (MAR) and Memory Data Register (MDR)?

Answer 9

MAR: Holds the memory address to be accessed.
MDR: Holds the data to be written to or read from memory.

Question 10

How does the memory read process work with MAR and MDR?

Answer 10

Load the MAR with the address of the data.
The data at that address is fetched and placed in the MDR.

Question 11

How does the memory write process work with MAR and MDR?

Answer 11

Load the MAR with the address and MDR with the data to be written.
The data is written to the address in MAR when the write signal is activated.

Question 12

What is the Program Counter (PC) in a computer system?

Answer 12

The Program Counter (PC) holds the address of the next instruction to be executed and is incremented after each instruction unless a control transfer instruction alters the flow.

Question 13

What are the two key properties of the Von Neumann model?

Answer 13

Stored program: Instructions and data are stored in the same memory.
Sequential instruction processing: Instructions are fetched and executed one at a time in sequential order unless altered by control flow instructions.

Question 14

What is the significance of sequential execution in the Von Neumann model?

Answer 14

Sequential execution means that the CPU fetches and executes instructions one after another, with the Program Counter (PC) advancing sequentially unless there is a branch or jump instruction.

Question 15

What is the stack in MIPS architecture, and how is it used?

Answer 15

The stack is a memory structure used to store temporary data, such as local variables, function arguments, and return addresses. It follows a Last-In-First-Out (LIFO) principle and grows downward in memory in MIPS architecture.

Question 16

What is the Stack Pointer (SP) in MIPS?

Answer 16

The Stack Pointer (SP) is a register that points to the top of the stack. In MIPS, it is used to manage function calls by saving and restoring register values to and from the stack.

Question 17

How does the stack grow in MIPS architecture?

Answer 17

The stack in MIPS architecture grows downward, meaning that the stack pointer (SP) is decremented when new data is pushed onto the stack.

Question 18

What are temporary registers in MIPS, and how are they used in relation to the stack?

Answer 18

Temporary registers (e.g., $t0–$t9) are used to hold intermediate values during calculations. In MIPS, there is no need to save them to the stack before a function call, as they are considered volatile and can be overwritten.

Question 19

What is an example of saving registers to the stack in MIPS assembly?

Answer 19

addi $sp, $sp, -12  # Allocate space for three registers on the stack
sw   $s0, 8($sp)    # Save $s0 to the stack
sw   $t0, 4($sp)    # Save $t0 to the stack
sw   $t1, 0($sp)    # Save $t1 to the stack

Question 20

What is the Write Enable signal in memory operations?

Answer 20

The Write Enable signal activates the writing process in memory, allowing data from the MDR to be written to the address specified in the MAR.