Computer Architecture Module 2
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Questions and Answers

What are the three main registers in a CPU?

Data registers, Address registers, and Control registers

What is the primary function of a data register?

To store data that the CPU is actively working with during processing, such as the result of a calculation

What is the main purpose of an address register?

To store the memory address of the location where data will be read from or written to.

Explain the role of a control register.

<p>To hold instructions and control signals that govern the actions and operations of the CPU.</p> Signup and view all the answers

The Accumulator register (AX) is frequently used for arithmetic and logical operations, as well as interacting with memory and input/output devices.

<p>True</p> Signup and view all the answers

The Base Register (BX) primarily functions with indirect addressing, enabling the CPU to access data located at an address contained within another register.

<p>True</p> Signup and view all the answers

The Count Register (CX) is primarily used for loop control, providing a way to keep track of the number of iterations in a loop.

<p>True</p> Signup and view all the answers

The Data Register (DX) is mainly associated with input/output operations, serving as a temporary holder for data being transferred to or from external devices.

<p>True</p> Signup and view all the answers

What is the purpose of segment registers like CS, DS, ES, and SS?

<p>To extend the addressing capability beyond the 64KB limit of the CPU by segmenting the memory into 64KB chunks.</p> Signup and view all the answers

What does the CS register specifically store?

<p>The starting address of the instruction segment.</p> Signup and view all the answers

Which register stores the starting address of the data segment?

<p>DS</p> Signup and view all the answers

Which register holds the starting address of the stack segment?

<p>SS</p> Signup and view all the answers

What does the ES register primarily point to?

<p>The starting address of the extra data segment.</p> Signup and view all the answers

What is the purpose of index registers like SI, DI, SP, and BP.

<p>They act as pointers within segments, providing offsets within a particular segment to pinpoint specific locations for data manipulation.</p> Signup and view all the answers

What is the function of the Source Index (SI) register?

<p>It holds the offset address within the data segment (DS) to access specific data.</p> Signup and view all the answers

What is the role of the Destination Index (DI) register?

<p>It holds the offset address within the extra data segment (ES) to locate data for processing.</p> Signup and view all the answers

What is the main function of the Stack Pointer (SP) register?

<p>It keeps track of the top of the stack, ensuring the correct location for storing and retrieving data.</p> Signup and view all the answers

What is the key purpose of the Base Pointer (BP) register?

<p>To access data within the stack segment without actually removing it from the stack.</p> Signup and view all the answers

Explain the role of the Instruction Pointer (IP) register.

<p>It determines the address of the next instruction that the CPU needs to fetch and execute.</p> Signup and view all the answers

What is the function of the Flags register?

<p>To store bits that reflect the current state of the CPU and indicate the outcome of arithmetic or logical operations.</p> Signup and view all the answers

Explain the purpose of the main memory in a computer system.

<p>Temporary storage for both programs and data, enabling the CPU to access information needed during processing.</p> Signup and view all the answers

Describe the structure of the main memory.

<p>It comprises a series of memory cells, organized in a 2-dimensional array, where each cell can hold a single bit of data.</p> Signup and view all the answers

What are the key components of the main memory.

<p>An address register, a word register, a local control unit, and a storage unit.</p> Signup and view all the answers

What is the main purpose of the address register in the main memory?

<p>To store the specific address of the memory location that is currently being accessed by the CPU.</p> Signup and view all the answers

Explain the role of the word register in the main memory.

<p>To temporarily hold the data that has been retrieved or is about to be stored in the main memory.</p> Signup and view all the answers

What is the function of the local control unit in the main memory?

<p>To manage the timing and control signals that govern the reading and writing of data in the main memory.</p> Signup and view all the answers

What is the core element of the storage unit in the main memory?

<p>The physical memory cells themselves, each capable of storing a single bit of information.</p> Signup and view all the answers

Calculate the size of main memory in bytes if the address register is 8 bits long and the word register is 4 bits long.

<p>128 bytes</p> Signup and view all the answers

What are the two main phases involved in fetching instructions in a CPU?

<p>The Fetch Cycle and the Execute Cycle.</p> Signup and view all the answers

Describe the Fetch Cycle.

<p>A sequence of operations where the CPU retrieves the next instruction to be executed from main memory, using the Program Counter (PC) to identify the correct location.</p> Signup and view all the answers

Explain the Execute Cycle.

<p>The stage where the CPU decodes the fetched instruction and then performs the operations specified by the instruction.</p> Signup and view all the answers

How does the Program Counter (PC) work during the Fetch Cycle?

<p>It holds the address of the next instruction that needs to be fetched from main memory.</p> Signup and view all the answers

What occurs during the Fetch Phase of the Instruction Cycle?

<p>The CPU retrieves the instruction from the memory location indicated by the Program Counter (PC).</p> Signup and view all the answers

What happens when the Instruction Register (IR) is loaded?

<p>The instruction is held in the IR for decoding and execution, essentially making it ready for processing.</p> Signup and view all the answers

What is the purpose of incrementing the Program Counter (PC) at the end of the Fetch Phase?

<p>To prepare for fetching the next instruction in the sequence by advancing the PC to the address of the subsequent instruction.</p> Signup and view all the answers

Explain the Execute Phase of the Instruction Cycle.

<p>The CPU analyzes the instruction by decoding it to understand what actions it needs to take and then sets up the necessary circuits within the CPU to perform the desired actions.</p> Signup and view all the answers

What are some common actions that may occur during the actual execution of an instruction in the Execute Phase?

<p>These include memory accesses, input/output operations, arithmetic calculations, logical operations and control flow modifications.</p> Signup and view all the answers

What is the role of buses in a computer system?

<p>They provide the communication pathways for transferring data, addresses, and control signals between different components, allowing the CPU to interact with memory, peripherals, and other parts of the system.</p> Signup and view all the answers

What are the three main types of buses?

<p>Address bus, Data bus, and Control bus.</p> Signup and view all the answers

What is the function of the address bus?

<p>To transmit memory or peripheral addresses from the CPU to other components, enabling the CPU to specify the location where data is stored or should be accessed.</p> Signup and view all the answers

Explain the role of the data bus?

<p>To transfer data between the CPU and other components of the system, including memory and peripheral devices, allowing the CPU to exchange information for processing and storage.</p> Signup and view all the answers

Describe the purpose of the control bus?

<p>To convey control signals and timing information between the CPU and other components, ensuring that operations are coordinated effectively and that data is transferred at the appropriate time.</p> Signup and view all the answers

The address bus is unidirectional, transmitting addresses only from the CPU to other components.

<p>True</p> Signup and view all the answers

The data bus is bidirectional, allowing the transfer of information in both directions between the CPU and other components?

<p>True</p> Signup and view all the answers

The control bus is unidirectional, sending out control signals and timing information from the CPU to other components.

<p>True</p> Signup and view all the answers

What are the primary functions of control lines in a computer system?

<p>They serve to coordinate the timing of operations, signal the start and end of data transfers, and manage the direction of data flow across buses.</p> Signup and view all the answers

Study Notes

Computer Architecture (Course Notes)

  • Course: Computer Architecture
  • Level: Second Year
  • Department: Computer Engineering
  • University: Al-Wataniya Private University
  • Instructor: Dr. Rouda Mehbany
  • Topic: Computer Architecture
  • Module: 2

Registers and General Structure

  • Registers: Essential components of the processor.

  • General Purpose Registers (AX, BX, CX, DX): Used for general-purpose data manipulation within the processor (much faster than interacting with memory).

    • AX (Accumulator): Preferred for arithmetic and logic operations, memory, input/output, and short programs.
    • BX (Base Register): Commonly used for indirect addressing. Has components BL (low 8 bits) and BH.
    • CX (Count Register): Used for loops, shifting, and rotating instructions, as well as counters in array applications.
    • DX (Data Register): Serves as input/output (I/O) pointer, and stores upper 16 bits in 32-bit division/multiplication operations.

  • General-Purpose Register Structure: Each register is 16 bits, composed of two 8-bit sections (High and Low). Example: BX has BH and BL sections.

Memory Segments (CS, DS, SS, ES)

  • Memory Addressing Limits: 8086 processors have a limited addressing range of 64KB per segment to access data and instructions in memory.
  • Segments: To access more than 64KB (e.g., the entire memory), the memory space is divided into segments (e.g., code segment (CS), data segment (DS), stack segment (SS), additional data segment (ES)).
  • Segment Registers: These registers (CS, DS, SS, ES) hold the starting addresses of each segment.
    • CS (Code Segment): Stores the starting address of executable code in memory.
    • DS (Data Segment): Stores the starting address of the program's data segment in memory.
    • SS (Stack Segment): Stores the starting address of the stack segment to store function calls and data.
    • ES (Extra Segment): Used for additional data segment in memory.

Index and Pointer Registers (SI, DI, SP, BP)

  • SI (Source Index): Used to deal with source data locations within DS memory segment. It stores the offset to access the data from the data section.
  • DI (Destination Index): Used to access data within the memory segment from address designated by register ES.
  • SP (Stack Pointer): Points to the top of the Stack Segment (SS) and is automatically updated when performing data pushes and pulls to the stack. Useful to locate and access data within the stack.
  • BP (Base Pointer): Points to a location within SS (Stack Segment). Used to easily access data in the stack without needing to retrieve it from the data segment.

Instruction Pointer (IP) and Flags Register

  • IP (Instruction Pointer): Points to the next instruction to be executed in a code segment. The BIU (Bus Interface Unit) automatically updates IP after each fetch.
  • Flags Register: Stores flags that provide status information and control aspects of the processor's execution. Consists of 16 bits, but primarily uses 9 bits.

Main Memory

  • Structure: Grid of cells where data and instructions are stored temporarily for processing and then sent out to outputs.
    • Word Register: Temporary data register associated with memory.
    • Control Unit: Manages reading/writing to memory.
  • Representation: Binary system is used to represent data.
  • Cell Types: Cells can be represented by switches (open/closed) or magnetic cells (current flow directions.)

Buses

  • Data Buses (Data Busses): Used to transfer data between the CPU and other components (bidirectional).

  • Address Buses: Carry the addresses of memory locations (unidirectional: to memory).

  • Control Busses: Convey control signals between the CPU and other parts (unidirectional).

  • Memory components: Various parts of the memory architecture are described through the use of diagrams with parts such as RAM, ROM, I/O, Memory Address Register (MAR), Control Unit (CU), and so on

  • Instruction Cycle: The general instruction cycle is presented, and the two main phases (i.e. fetch and execute) are included in the summary

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Description

This quiz covers essential concepts in Computer Architecture, focusing on registers and their roles within the processor. Students will explore general-purpose registers including AX, BX, CX, and DX. Understanding these components is crucial for effective data manipulation and performance optimization in computer systems.

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