Computer Architecture I/O Module Quiz
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Questions and Answers

What is the primary disadvantage of programmed I/O?

It wastes CPU time since the CPU waits for the I/O module to complete the operation.

How does the I/O module communicate its status to the CPU in programmed I/O?

The I/O module sets status bits that the CPU checks periodically.

What role does the I/O module play in the relationship between the CPU and external devices?

The I/O module acts as an intermediary, performing operations on the devices and managing status and data transfer.

What are the types of I/O commands issued by the CPU to the I/O module?

<p>The I/O commands include Control, Test, Write, and Read.</p> Signup and view all the answers

What is one key decision an I/O module must make regarding device properties?

<p>An I/O module must decide whether to hide or reveal device properties to the CPU.</p> Signup and view all the answers

What role does the I/O module play in a computer's architecture?

<p>The I/O module interfaces with the processor and memory via the system bus and connects to peripheral devices through tailored data links.</p> Signup and view all the answers

Name and describe the three categories of external devices connected to an I/O module.

<p>The three categories are human-readable devices (e.g., screen, printer, keyboard), machine-readable devices (e.g., magnetic disk, sensors), and communication devices (e.g., modems).</p> Signup and view all the answers

Why can't high-speed system buses be used to communicate directly with peripherals?

<p>High-speed system buses cannot handle the varying data transfer rates and formats of different peripherals effectively.</p> Signup and view all the answers

What types of data might be exchanged between an I/O module and an external device?

<p>Control signals, status information, and actual data are the types of information exchanged between an I/O module and external devices.</p> Signup and view all the answers

How does the data transfer rate mismatch between peripherals and the processor/memory affect system design?

<p>The mismatch necessitates the use of I/O modules to mediate communication, as direct connection could bottleneck performance.</p> Signup and view all the answers

What is the main function of an I/O module in interpreting address lines?

<p>To determine if a command is intended for itself based on the address lines.</p> Signup and view all the answers

Describe the key difference between memory-mapped I/O and isolated I/O.

<p>Memory-mapped I/O shares an address space with memory, while isolated I/O has separate address spaces.</p> Signup and view all the answers

Explain how interrupt-driven I/O improves CPU efficiency.

<p>It allows the CPU to perform other tasks while the I/O module handles data transfer and interrupts when ready.</p> Signup and view all the answers

What steps does the CPU take when it receives an interrupt from an I/O module?

<p>The CPU saves its context and processes the interrupt to fetch and store data from the I/O module.</p> Signup and view all the answers

How can a system identify which device has issued an interrupt?

<p>By using interrupt request lines or identifying the source through software or hardware mechanisms.</p> Signup and view all the answers

What is the impact of DMA on CPU performance during data transfers?

<p>DMA allows for more efficient data transfers by letting the CPU execute other instructions while the transfer is occurring, thus improving overall performance.</p> Signup and view all the answers

How does a single-bus integrated DMA controller differ from a detached DMA controller in terms of bus usage?

<p>A single-bus integrated DMA controller uses the bus once per transfer, while a detached DMA controller uses the bus twice for each transfer.</p> Signup and view all the answers

Explain the role of the I/O controller in modern computer systems.

<p>The I/O controller manages data transfers between I/O devices and memory, thus offloading the CPU and improving system speed.</p> Signup and view all the answers

What evolutionary changes have occurred in I/O channels regarding CPU involvement?

<p>I/O channels have evolved to perform more functions without CPU intervention, allowing the CPU to dedicate its resources to processing tasks.</p> Signup and view all the answers

Describe the efficiency benefits of using a separate I/O bus in DMA configurations.

<p>A separate I/O bus allows for direct communication between DMA-enabled devices and memory, utilizing the bus once per transfer and resulting in less CPU suspension.</p> Signup and view all the answers

What are the maximum data transfer speeds for USB 3.0 and USB 3.1?

<p>USB 3.0 supports data transfer speeds up to 4 Gbps, while USB 3.1 supports speeds up to 9.7 Gbps.</p> Signup and view all the answers

How many devices can be connected in a FireWire daisy chain configuration?

<p>Up to 63 devices can be connected in a FireWire daisy chain configuration.</p> Signup and view all the answers

What are the two types of transmission methods used in the FireWire link layer?

<p>The two types of transmission methods in the FireWire link layer are asynchronous and isochronous.</p> Signup and view all the answers

What is the primary purpose of InfiniBand in computing environments?

<p>InfiniBand is an I/O specification aimed at high-end servers for efficient data transmission.</p> Signup and view all the answers

What role does the root play in FireWire's arbitration scheme?

<p>In FireWire's arbitration scheme, the root acts as the arbiter, determining which devices get data transmission priority.</p> Signup and view all the answers

What are two key advantages of using InfiniBand in server architecture?

<p>Increased capacity and flexibility are two key advantages of using InfiniBand in server architecture.</p> Signup and view all the answers

How does InfiniBand manage data traffic during transfers?

<p>InfiniBand manages data traffic by mapping incoming traffic to outgoing lanes through its switch architecture.</p> Signup and view all the answers

Explain the role of virtual lanes in InfiniBand operations.

<p>Virtual lanes in InfiniBand operations are used for data transfer, with one lane allocated for management and the others for data traffic.</p> Signup and view all the answers

What is the maximum distance allowed for I/O connections using single-mode fiber in InfiniBand?

<p>The maximum distance allowed for I/O connections using single-mode fiber in InfiniBand is 10 km.</p> Signup and view all the answers

Describe the three principal I/O techniques mentioned in the content.

<p>The three principal I/O techniques are programmed I/O, interrupt-driven I/O, and direct memory access (DMA).</p> Signup and view all the answers

Study Notes

Input/Output (I/O)

  • I/O involves peripherals with various operation methods
  • There's a mismatch between peripheral data transfer rates and memory/processor rates
  • Peripherals often use different data formats and word lengths than the computer itself

I/O Module

  • Functions as an intermediary between the processor and memory and peripherals
  • Interfaces to the processor and memory via the system bus or central switch
  • Interfaces to one or more peripheral devices

External Devices

  • Provide a means of exchanging data between the external environment and the computer
  • An external device attaches to the computer via a link to an I/O module
  • The link exchanges control, status, and data between the I/O module and the external device
  • Often referred to as a peripheral device

External Device Categories

  • Human-readable: Suitable for communication with the user (e.g., screen, printer, keyboard)
  • Machine-readable: Suitable for communication with equipment (e.g., magnetic disk, tape system, sensors, actuators)
  • Communication: Suitable for communication with remote devices (e.g., modem, network interface card (NIC))

External Device Block Diagram

  • Control signals: Determine the device's function (e.g., read/write, report status, etc.)
  • Control logic: Processes and interprets control signals to the device
  • Buffer: Temporarily holds data during transfer between the I/O module and the environment
  • Transducer: Converts data from one form (electrical) to another form (e.g., mechanical, thermal)

I/O Module

  • Control & Timing: Coordinates flow between internal and external resources. Handles device communication (commands, status, data).
  • Data Buffering: Handles high CPU/memory transfer rates, often vastly slower peripheral rates.
  • Error Detection: Monitors peripheral for mechanical/electrical malfunctions

CPU Communication

  • Command decoding: I/O module accepts commands from the processor
  • Data transfers: Data exchanged between the processor and I/O module via the data bus.
  • Status reporting: Key for peripherals that are slow, status information is critical for the I/O module.
  • Address recognition: I/O module identifies the device with a unique address for control.

I/O Steps

  • CPU checks I/O module's device status
  • I/O module returns its status
  • CPU requests data
  • I/O module gets data from device
  • I/O module sends data to CPU

I/O Module Decisions

  • Hide or reveal device properties to CPU.
  • Support multiple or single devices
  • Control device functions or leave for CPU.
  • Operating System (O/S) decisions on how devices are treated (e.g. Unix treats peripherals as files).

I/O Operation Techniques

  • Programmed I/O: CPU directly controls I/O, waits for each operation to complete

  • Interrupt-driven I/O: CPU issues a command, then moves on to other tasks; CPU gets interrupted when device is ready

  • Direct Memory Access (DMA): DMA controller handles transfer between memory and peripheral without continuous CPU intervention

I/O Commands

  • Issued by the CPU to the I/O module.
  • Identifies the module and any specific device as required via addresses
  • Includes I/O commands for control (e.g., disc spin-up), test, read, and write processes

I/O Instructions

  • Executed by the processor; tightly coupled with the I/O commands.
  • The form of the instructions depends on how the external devices are addressed

Addressing I/O Devices

  • Programmed I/O data transfers mimic memory access
  • Each device gets a unique identifier (address)
  • CPU commands contain the identifier for the device

Addressing Modes

  • Memory-mapped I/O: Devices and memory share the address space
  • Isolated I/O: Separate address spaces, specialized commands

Interrupt-Driven I/O

  • Overcomes CPU waiting
  • I/O module interrupts CPU when ready.
  • No need to repeatedly monitor the device

DMA (Direct Memory Access)

  • Interrupt driven and programmed I/O require active CPU intervention
  • DMA is the answer to faster transfer speeds, taking over system control from the processor for transfers
  • DMA controller uses the bus only when the processor does not, possibly causing temporary suspension (cycle stealing)

DMA Functions

  • Additional module on the system bus
  • DMA controller takes over I/O functions from the CPU

DMA Operations

  • CPU tells the DMA controller on the type of read/write, the device address and the memory block address where to write or read data.
  • CPU continues with other tasks whilst DMA manages data transfers between peripheral and memory.
  • DMA controller sends interrupt when finished.

DMA Cycle Stealing

  • DMA takes control of the bus for a cycle
  • Transfer of data without an interrupt
  • CPU suspended temporarily

DMA Configurations

  • Single-bus: DMA controller detached, using the bus twice for each transfer, CPU is suspended twice
  • Single-bus, Integrated: DMA controller integrated with I/O using the bus only once for each transfer, CPU is suspended once.
  • Separate I/O bus: Separate I/O bus, the bus is used only once for each transfer, CPU is suspended only once

I/O Channels

  • As systems evolve, I/O devices become more complex and I/O channels allow for an improved transfer speed and reduced burden on the CPU.
  • This can take over the entire I/O from the CPU.
  • I/O controllers respond to I/O instructions and execute them.
  • Selector channel: Controls multiple high-speed devices at the same time and on a single transfer.
  • Multiplexor channel: Designed for handling multiple low-speed devices; can serve multiple devices rapidly

Interfacing

  • Parallel interfaces: Multiple data lines connect the I/O module to the peripheral; bits are transferred simultaneously. (e.g., tape and disc drives)
  • Serial interfaces: Only one data line used to transfer data sequentially. (e.g., printers)

Interfacing: I/O Modules and External Devices

  • Point-to-point: Dedicated link between the I/O module and the external device (e.g., keyboard, printer).
  • Multipoint: Used to support mass storage devices (such as disk and tape drives), and multimedia devices (such as CD-ROMs). Includes examples like FireWire and Infiniband.

External Interconnection Standards

  • Various standards exist for connecting external devices, including USB, FireWire, SCSI, Thunderbolt, InfiniBand, PCI Express, SATA, Ethernet, and Wi-Fi

USB

  • Widely used for connecting peripherals.
  • Multiple generations exist with increasing data rates.

IEEE 1394 FireWire

  • High-performance, low-cost serial bus.
  • Common in digital cameras, VCRs, and TVs
  • Daisy chain or tree-structured configuration, up to 63 devices.
  • Layers (physical, link, transaction)

FireWire Configuration

  • Daisy-chain up to 63 devices on one port
  • Up to 1022 buses via bridges (tree configuration).
  • Automatic configuration.

FireWire 3 Layer Stack

  • Physical layer: Transmission medium
  • Link layer: Packets
  • Transaction layer: Requests and responses

FireWire Protocol Stack

  • Layers define how data is organized for transmission and handling across the FireWire system

FireWire - Physical Layer

  • Data rates range from 25 to 400 Mbps
  • Uses tree-based arbitration, with root acting as arbiter
  • Arbitration methods include fair, urgent, and first-come, first-served

FireWire - Link Layer

  • Two transmission types: Asynchronous and isochronous
  • Asynchronous: Variable-length data packets
  • Isochronous: Fixed-size data packets at regular intervals

InfiniBand

  • High-end server I/O specification
  • High capacity, expandability, flexibility
  • Replaces PCI in servers.
  • Supports up to 30Gbps

InfiniBand Architecture

  • Remote storage, network connections between servers.
  • Higher server density
  • Scalable data centres
  • Long distances using fiber optics (up to 10 km)

InfiniBand Operations

  • 16 logical channels (virtual lanes) per physical link.
  • One channel for management, others for data
  • Data transmitted as packets, virtual lane for temporary transfers to end-points.
  • Switches map incoming to outgoing lanes.

Summary

  • I/O architecture enables interaction with the outside world.
  • Three main I/O techniques: programmed, interrupt-driven, and direct memory access (DMA). Each technique is suited to specific needs and workloads relating to the CPU.

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Bic10503 Comp Arch Chapter 4: Input/Output PDF

Description

Test your knowledge on the role and functioning of I/O modules in computer architecture. This quiz covers their interaction with the CPU, types of commands, and the impact on system design. Dive into the intricacies of programmed I/O and peripheral communication.

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