Computer Architecture Addressing Modes Quiz

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Questions and Answers

What is a primary advantage of immediate addressing mode?

It avoids any memory reference for the operand. (correct)

It can store large numbers efficiently.

It allows for complex data structures.

It allows for dynamic memory allocation.

What is a disadvantage of immediate addressing mode?

The size of the operand is limited by the address field. (correct)

It requires more cycles for operand retrieval.

The operand is storied in the instruction fetch.

It uses a significant amount of cache memory.

In immediate addressing mode, what form is the operand typically stored in?

Floating point representation

Hexadecimal format

Two's complement form (correct)

Unsigned representation

Which addressing mode can be used to define and use constants effectively?

Immediate mode Signup and view all the answers

What is the role of the leftmost bit in the operand field in immediate addressing?

It serves as the sign bit. Signup and view all the answers

What is a primary advantage of register addressing?

It requires no memory references. Signup and view all the answers

How does register indirect addressing differ from indirect addressing?

It refers to a register instead of a memory location. Signup and view all the answers

In displacement addressing, what does the effective address (EA) represent?

The sum of a direct address and a register value. Signup and view all the answers

What limits the address space in register addressing?

The size of the register itself. Signup and view all the answers

What is a common application of displacement addressing?

Relative addressing. Signup and view all the answers

What is one disadvantage of register addressing?

The address space is very limited. Signup and view all the answers

What structure is primarily used for stack addressing?

A linear array of locations Signup and view all the answers

What type of queue is associated with stack addressing?

Last-in-first-out queue Signup and view all the answers

What does the notation EA = (R) in register indirect addressing signify?

The effective address is derived from a register value. Signup and view all the answers

What is the primary function of the program counter (PC) in relative addressing?

Maintains the address of the next instruction Signup and view all the answers

Which address type requires at least two address fields in its instruction?

Displacement addressing. Signup and view all the answers

How is the stack pointer maintained in a stack addressing scheme?

In a register Signup and view all the answers

What does the effective address (EA) equal in direct addressing?

Address field (A) Signup and view all the answers

What type of addressing is primarily used in branch instructions?

Immediate addressing Signup and view all the answers

How does the address field in relative addressing typically represent the displacement?

As a two's complement number Signup and view all the answers

What is a key advantage of indirect addressing compared to direct addressing?

Provides a larger address space Signup and view all the answers

What is a significant advantage of base-register addressing?

It conveniently implements segmentation and maintains locality Signup and view all the answers

What is the effective address range for branch instructions in ARM architecture?

± 32MB from the program counter Signup and view all the answers

Which of the following is a disadvantage of indirect addressing?

Execution requires two memory references Signup and view all the answers

In indexing, what does the referenced register typically contain?

A positive displacement from the referenced address Signup and view all the answers

What does 'autoindexing' refer to in indexing addressing mode?

Incrementing or decrementing the index register after each reference Signup and view all the answers

What happens in multilevel or cascaded indirect addressing?

Three or more memory references may be required Signup and view all the answers

What is a limitation of direct addressing?

It provides low address space Signup and view all the answers

What distinguishes postindexing from preindexing in indexing addressing?

Postindexing occurs after the indirection is completed Signup and view all the answers

What implication does locality have in relative addressing?

It reduces the number of address bits needed Signup and view all the answers

In indirect addressing, how is the effective address (EA) represented?

As the contents of memory location Signup and view all the answers

Which addressing method is more efficient in terms of memory references?

Direct addressing Signup and view all the answers

What is an implicit register reference in base-register addressing?

The use of a segment base register without explicit instruction Signup and view all the answers

For a word length of N, what is the address space available in indirect addressing?

$2^N$ Signup and view all the answers

What is the main enhancement introduced by the Thumb-2 instruction set in Cortex-M microcontrollers?

It allows for intermixed 32-bit and 16-bit instructions. Signup and view all the answers

How does Thumb-2 instruction set affect code density compared to the original Thumb?

It has comparable overall code density to Thumb. Signup and view all the answers

What is a key feature of most 32-bit Thumb instructions in Thumb-2?

They are all unconditional. Signup and view all the answers

What does the If-Then (IT) instruction in Thumb-2 provide?

Functionality similar to ARM's condition field. Signup and view all the answers

Before Thumb-2, developers faced a trade-off between which two aspects?

Code size and performance. Signup and view all the answers

What characteristic is NOT typically associated with ARM instructions compared to Thumb-2 instructions?

Reduced performance levels. Signup and view all the answers

Which addressing mode is NOT associated with ARM instruction formats?

Symbolic addressing. Signup and view all the answers

What is a major benefit of using the Thumb-2 instruction set for developers?

It combines the advantages of smaller size and better performance. Signup and view all the answers

Study Notes

Instruction Sets: Addressing Modes and Formats

Instruction sets define how instructions are structured and how operands are accessed.
Addressing modes determine how the operands of an instruction are located.

Addressing Modes

Immediate Addressing: The operand's value is included directly within the instruction.
- Advantage: No memory access is needed beyond fetching the instruction.
- Disadvantage: Limited operand size.
Direct Addressing: The operand's address is included in the instruction.
- Advantage: Single memory access for operand retrieval.
- Disadvantage: Limited address space.
Indirect Addressing: The instruction contains the address of a memory location that, in turn, contains the address of the actual operand.
- Advantage: Large address space can be accessed.
- Disadvantage: Requires multiple memory accesses.
Register Addressing: The operand is held in a register.
- Advantage: Fast access to operands.
- Disadvantage: Limited address space; requires multiple registers to address a full memory.
Register Indirect Addressing: The instruction contains the address of a register that holds the address of the operand.
- Advantage: Increased address space without increasing the instruction size.
- Disadvantage: Extra memory reference for operand retrieval.
Displacement Addressing: The operand's address is calculated by adding a displacement value to the content of a register.
- Advantage: Flexibility in addressing memory locations; often used in loops; often used with base registers.
- Disadvantage: More complex address calculation.
Stack Addressing: Operands are pushed onto and popped off a stack.
- Advantage: Implicit addressing; efficient for function calls, recursion.
- Disadvantage: Limited applicability to specific programming tasks.

Instruction Formats

Instructions are encoded into bits.
Opcode: The part of the instruction specifying the operation to be performed.
Operands: Data values or memory locations referenced by the instruction.
Addressing mode fields: Specifying how operands are found.
Instruction format defines a layout for bits of an instruction in terms of its constituent fields.
- Most instruction sets have multiple formats.

Instruction Length

Instruction length affects and is affected by memory size, memory organization, bus structure, processor complexity, and speed.
The length should be a multiple of character length or the memory transfer length or multiple both. This is important for efficient data transfers.

Allocation of Bits

Addresses bits need to be allocated for various components of an instruction.
Number of bits for addressing modes, number of operands, range, and granularity.

ARM and x86 Instruction Formats

Specific formats for ARM and x86 architectures.

Variable-Length Instructions

Variable-length instructions can be efficiently stored.
They increase processor complexity because fetching the next instruction is complicated.
Length of next instruction isn't known in advance so strategy of fetching more than one instruction must be used.

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Description

Test your knowledge on various addressing modes in computer architecture with this comprehensive quiz. Questions cover immediate, register, indirect, and displacement addressing, along with their advantages and disadvantages. Perfect for students studying computer organization and architecture.