Architecture of Computers 2, Chapter 4: Interruptions & I/O

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Questions and Answers

What is a microprocessor and its role in a computing system?

A microprocessor is an integrated circuit that performs all the operations of a central processing unit (CPU).

What company was the first to successfully integrate all the components of a processor onto a single integrated circuit?

Intel

The Intel 4004 microprocessor was the first microprocessor ever made.

True

What is the primary purpose of an interrupt in a computer system?

To temporarily suspend the execution of a program and handle a specific event Signup and view all the answers

What are the two main categories of interrupts?

Software and Hardware Signup and view all the answers

What does NMI stand for in the context of computer interrupts and what is its significance?

NMI stands for Non-Maskable Interrupt. Signup and view all the answers

Software interrupts are caused by exceptional conditions or instructions within a program.

True Signup and view all the answers

The Intel 4004 microprocessor was capable of processing 16 bits.

False Signup and view all the answers

What is the main solution discussed to lower power consumption and increase computational power in modern CPUs?

Increasing the number of cores and decreasing the clock speed Signup and view all the answers

What is the purpose of the interrupt vector table in a computer system?

The interrupt vector table stores the addresses of interrupt handlers, allowing the CPU to quickly locate and execute the appropriate routine when an interrupt occurs. Signup and view all the answers

What is the main purpose of the INT N instruction in assembly language?

The INT N instruction generates a software interrupt, which triggers the execution of a specific interrupt handler associated with the interrupt number N. Signup and view all the answers

What is the significance of the AH register when using the INT 21H interrupt?

The AH register holds the function code specifying which specific service the INT 21H interrupt needs to execute. Signup and view all the answers

Which instruction is generally used to send a byte of data to a specific output port?

The OUT instruction is used to send data to an output port. Signup and view all the answers

Describe two major techniques for handling input/output (I/O) operations in computer systems.

The two major techniques for handling I/O operations are programmed I/O (polling) and interrupt-driven I/O. Signup and view all the answers

Programmed I/O is generally considered more efficient than interrupt-driven I/O.

False Signup and view all the answers

What is the main idea behind diverting an interrupt?

Diverting an interrupt involves modifying the interrupt vector table to change the interrupt handler associated with a specific interrupt number, effectively altering how the system responds to that particular event. Signup and view all the answers

What does the acronym 'C.I' commonly refer to in the context of computer systems?

C.I stands for 'Circuit Interface.' Signup and view all the answers

In the context of programmed I/O, 'polling' refers to the CPU constantly checking the status of peripheral devices to see if they are ready to exchange data.

True Signup and view all the answers

What is the primary advantage of interrupt-driven I/O over programmed I/O?

The main advantage of interrupt-driven I/O is that it allows the CPU to perform other tasks while waiting for peripheral devices to become ready, making it more efficient than programmed I/O where the CPU must constantly poll devices. Signup and view all the answers

In the context of input/output (I/O) operations, what is the difference between an 'input port' and an 'output port'?

An input port is used by the CPU to receive data from a peripheral device, while an output port is used by the CPU to send data to a peripheral device. Signup and view all the answers

What is the role of the 'control port' in the context of input/output (I/O) operations?

The control port is used by the CPU to configure and manage the operation of the associated interface circuit (C.I). Signup and view all the answers

Describe two main benefits of using interrupt-driven I/O in computer systems.

Using interrupt-driven I/O offers two main benefits: Firstly, it frees up the CPU to perform other tasks while waiting for I/O devices to become ready, leading to increased efficiency. Secondly, it allows peripheral devices to signal their readiness for data transfer directly to the CPU, avoiding the need for continuous polling and reducing system overhead. Signup and view all the answers

Explain the significance of the 'status port' in the context of input/output operations.

The status port provides the CPU with information on the current state of the associated interface circuit (C.I) and connected peripheral device. Signup and view all the answers

Study Notes

Architecture of Computers 2, L2ING, Chapter 4: Interruptions & I/O

Microprocessor Definition: A microprocessor is an integrated circuit capable of executing all the operations of a central processing unit.
Intel's 1971 Achievement: In 1971, Intel successfully placed all the components of a processor onto a single integrated circuit, creating the first microprocessor.
Key Figures: The development was a collaborative effort, notably by Marcian Ted Hoff and Federico Faggin.
First Intel Microprocessor: The Intel® 4004 microprocessor was introduced in 1971.
Historical Microprocessor Characteristics: The Intel 4004 had 2300 transistors and worked with 4-bit calculations, 16 registers with 4 bits of data and 46 instructions.
Processor Data Bus Width: The 4004's data bus was 4 bits wide.
Clock Speed: The processor had a clock speed of 108 kHz.
Microprocessor Size (4004): The chip's dimensions were 3.81mm by 2.79mm, equalling 10.62mm²
Cost: Intel sold the 4004 and its rights for US$ 60,000 to its client, the Japanese company Busicom.
Evolution of Microprocessors: The provided table shows a chronological list of Intel microprocessors with increasing clock speeds and transistor counts.

Historical Evolution

Timeline and Specifications: Displays a comprehensive table of Intel processor releases, noting their respective dates, model names, transistor counts, manufacturing process nodes (fineness of engraving), and clock frequencies.

Interruptions

Asynchronous Event: It's a temporary suspension of the currently running program.
Branching to Subprogram: Causes the processor to branch to a specific subroutine (interrupt routine) to handle the interruption.
Return Instruction (IRET): Essential to return and resume the main program's execution.

Interruption Classes

Material Interrupts (IRQ): Caused by external events from peripherals such as input devices, output devices, that trigger them via electrical signals.
- Non-Maskable Interrupt (NMI): Not influenced by the IF flag.
- Interrupt Request (INTR): Its execution depends on the IF flag.
Software Interrupts: Triggered by special instructions within the microprocessor's instruction set, or by abnormal or logical conditions.
- Vectorized Interrupts (x86 Intel): x86 Intel microprocessors use a vectorized approach for interrupt handling. The physical addresses of the interrupt handlers are saved in a table.
- Interrupt Vector Table: A system table containing addresses (CS:IP) to execute every possible interrupt handler.
  - Reserved Vectors: The first 5 vectors are reserved by Intel for specific uses. Others are assigned by the operating system.
  - User Space: The remaining, empty vectors can be used by the operating system or the user.

Interrupt 21H

System Interrupt: A significant interrupt routine offering various services.
AH Register: You must first set the function number in the AH register, before directing the interrupt.

I/O Operations (Inputs/Outputs)

Input/Output (I/O) Operations: Enable data exchange between the microprocessor and peripheral devices through interface circuits.
Interface Circuit: A device-specific circuit responsible for managing data transmission between a microprocessor and a peripheral device and controlling the data transfer.
- Characteristics of ICs: ICs are usually programmable and intelligent, capable of supporting various operation modes.

I/O Types

Programmed I/O (Polling): The microprocessor continuously interrogates the status of an interface to detect when it is ready for a given operation.
Interrupts: The interface signals the microprocessor when it's ready for data transfer.

Specific I/O Instructions

IN: Instruction for reading data from a port, into registers, such as AL or AX.
OUT: Instruction for writing data from a register into a port.

Example I/O Operations

Examples and Solutions: Some programming examples in assembly language are given to illustrate diverse I/O operations, such as reading an input from the keyboard and writing to a display.

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Description

Explore the intricacies of Interruptions and I/O systems as outlined in Chapter 4 of Architecture of Computers 2. Learn about the evolution of microprocessors, particularly the Intel 4004, and its pivotal role in computing history. This quiz will test your understanding of microprocessor definitions, characteristics, and key figures in the development of this technology.