Computer Architecture Fundamentals

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Questions and Answers

What is the primary function of input devices in a computer system?

To convert input data into internal signals for processing (correct)

To display the results of operations to the user

To permanently store data and instructions

To execute the programs in a random sequence

Why is memory considered crucial in a computer system?

It permanently stores all the applications

It manages communication between the CPU and external devices

It temporarily holds both instructions and data for execution (correct)

It receives inputs directly from the user

Which register specifies the address in memory for the next read or write operation?

I/O buffer register (I/OBR)

Memory address register (MAR) (correct)

I/O address register (I/OAR)

Memory buffer register (MBR)

What role does the I/O buffer register (I/OBR) play in a computer system?

It facilitates the transfer of data between I/O modules and the CPU Signup and view all the answers

How does the CPU interact with memory during data processing?

It uses registers to read and write data to specific memory addresses Signup and view all the answers

What is a key characteristic of the memory module in a computer?

It consists of sequentially numbered addresses each holding a binary number Signup and view all the answers

What does the I/O address register (I/OAR) do?

It specifies which I/O device to communicate with Signup and view all the answers

What is the primary function of a computer?

To execute a program consisting of instructions Signup and view all the answers

How does a program execution differ from simple data processing?

Execution may require jumping between different data elements Signup and view all the answers

Which component of the computer is responsible for performing the actual execution of instructions?

Processor Signup and view all the answers

In the context of instruction processing, which of the following steps is performed first?

Reading the instruction from memory Signup and view all the answers

What is a primary purpose of interrupts in processing?

To improve processing efficiency by allowing the processor to perform other tasks. Signup and view all the answers

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

Tracks the address of the next instruction to be executed Signup and view all the answers

What problem can arise when the processor continually waits for an external device?

The processor may waste many instruction cycles not involving memory. Signup and view all the answers

Which of the following registers temporarily holds data being transferred to or from memory?

Memory Buffer Register (MBR) Signup and view all the answers

Which of the following describes the first step of the I/O program as mentioned?

Preparing parameters and copying data to a buffer. Signup and view all the answers

How does program execution proceed in a computer system?

By repeating the process of fetch and execution of instructions Signup and view all the answers

What is the function of the Instruction Register (IR)?

To hold the instruction currently being executed Signup and view all the answers

What does the term 'WRITE calls' refer to in this context?

Requests made by a user program to perform I/O operations. Signup and view all the answers

What is the value loaded into the instruction register (IR) during the first fetch cycle?

1940 Signup and view all the answers

What is a consequence of issuing an I/O command without using interrupts?

The program becomes entirely dependent on the I/O device's speed. Signup and view all the answers

Which component is essential for transferring data between different parts of the computer system?

System bus Signup and view all the answers

Which part of the instruction in the IR indicates that the accumulator (AC) is to be loaded?

The first 4 bits Signup and view all the answers

How many instruction cycles are needed to add the contents of memory locations 940 and 941?

Three Signup and view all the answers

Which of the following could describe a processor that requires fewer cycles for executing complex instructions?

Includes instructions with multiple addresses Signup and view all the answers

In the instruction expressed as ADD B,A in the PDP-11 processor, what is the final storage location of the result?

Memory location A Signup and view all the answers

Why must the processor have at least two registers when executing the ADD instruction in the PDP-11?

To prevent loss of data in memory location A Signup and view all the answers

What happens during the execution cycle after the first instruction is fetched?

The contents of location 940 are loaded into the accumulator Signup and view all the answers

What is an example of an I/O operation mentioned for complex instructions?

Fetching data from a peripheral device Signup and view all the answers

What happens when an interrupt occurs during the execution of a program?

The processor saves the current program's context and switches to the interrupt handler. Signup and view all the answers

In the interrupt cycle, what does the processor check first?

If there are any pending interrupts. Signup and view all the answers

What does the processor do with the program counter during an interrupt?

Sets it to the starting address of the interrupt handler routine. Signup and view all the answers

What is referred to as 'saving the context' in the process of handling an interrupt?

Saving the next instruction address and processor data. Signup and view all the answers

What indicates to the processor that an interrupt signal is present?

An external device signaling the CPU. Signup and view all the answers

What is the state of interrupts during the process of checking for pending interrupts?

Interrupts are enabled so they can be checked. Signup and view all the answers

During the fetch cycle after an interrupt has been processed, what does the processor do next?

Resumes the interrupted program with the saved context. Signup and view all the answers

What happens if no interrupts are pending during the interrupt cycle?

The processor fetches the next instruction of the current program. Signup and view all the answers

What is the primary purpose of the Interrupt Acknowledge command?

To read an interrupt identifier from an interrupt controller Signup and view all the answers

Which command is used to transfer data between the initiator and an I/O controller?

I/O Read Signup and view all the answers

What does the Memory Write and Invalidate command guarantee?

At least one cache line is written back to memory Signup and view all the answers

In the context of PCI commands, what is a Special Cycle used for?

To broadcast messages to targets Signup and view all the answers

How do Memory Read commands primarily transfer data?

In terms of cache lines or blocks Signup and view all the answers

What is indicated by the byte enable lines during the Interrupt Acknowledge command?

The size of the interrupt identifier to be returned Signup and view all the answers

Which command enables a master to update configuration parameters in PCI devices?

Configuration Write Signup and view all the answers

Which of the following commands is specifically designed for reading a burst of data?

Memory Read Line Signup and view all the answers

Study Notes

Chapter 3: A Top-Level View of Computer Function and Interconnection

Computer components include the processor, main memory, and I/O modules, interconnected to execute programs
Instruction cycle involves fetching instructions, operands, storing operands, and interrupt checks (if enabled)
Key bus design elements include arbitration (centralized or distributed permission to send signals), timing (synchronized to a clock or asynchronous), and width (address and data lines)

3.1 Computer Components

Von Neumann architecture is the foundation for virtually all contemporary computer designs, based on three key concepts
- Data and instructions are stored in a single, addressable memory
- Execution occurs sequentially (unless explicitly modified)
- Programs are stored in the same memory location as data

3.2 Computer Function

Computer function is primarily program execution, which consists of a sequence of instructions stored in memory that the processor executes
Instruction cycle involves fetch and execute cycles, with
- Processor-memory transfers (data movement)
- Processor-I/O transfers (data exchange with external devices)
- Data processing (arithmetic/logical operations)
- Control (changing the flow of execution)
Instruction cycle includes:
- Instruction fetch: Fetching instruction from memory into the instruction register (IR)
- Instruction decoding (interpreting opcode): determining the type of operation and operands
- Operand address calculation (if necessary): Locating the operands in memory or I/O
- Operand fetch: Retrieving the operands from memory or I/O
- Data operation (performing the operation): Doing the specified computation
- Operand store (writing the result): Storing the result to memory or I/O
Interrupts: An external event that can suspend the current program’s execution

3.3 Interconnection Structures

Interconnection structures connect computer components (processor, memory, I/O)
Communication pathways allow for data and control signals exchange between modules
Bus structures (e.g., system bus, expansion buses) facilitate efficient data exchange, composed of data lines, address lines, and control lines
Bus characteristics
- Type (dedicated or multiplexed)
- Arbitration method (centralized or distributed)
- Timing (synchronous or asynchronous)
- Width (data and address lines)
- Data transfer types

3.4 Bus Interconnection

Bus is a shared communication pathway
Buses consist of multiple lines for parallel data transmission
Functional bus components include:
- Data lines: To transfer data between modules
- Address lines: To specify the source or destination of data on the data bus
- Control lines: To control the bus access mechanisms and operations

3.5 PCI (Peripheral Component Interconnect)

PCI is a high-bandwidth, processor-independent bus
PCI structure facilitates high-speed I/O operations
PCI bus structure: System pins (like clock and reset), address and data pins, interface control pins, arbitration mechanisms, and other specialized signal lines
PCI Commands
- Interrupt Acknowledge
- Special Cycle
- I/O Read and Write
- Memory Read and Write
- Configuration Read and Write

3.6 Recommended Reading and Web Sites

Recommended reading and web resources for further study on PCI bus specifications and details

3.7 Key Terms, Review Questions, and Problems

Key terms related to computer components and their interconnection
Review questions related to the material for practice
Problems for practical application

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Description

Test your knowledge on the essential functions and components of computer architecture. This quiz covers key concepts such as input devices, memory functions, registers, and the role of the CPU in processing data. Ideal for students eager to understand the basic principles of how computers operate.