Computer Hardware - I/O Devices PDF

Computer Hardware Components Recall Input and Output Devices I/O Technology Input Devices What Is Input? Keyboard Pointing devices Touch screens Pen input Motion input Voice input Video input Scanners and reading devices Keyboards Keyboards Dome Swit...

Computer Hardware Components Recall Input and Output Devices I/O Technology Input Devices What Is Input? Keyboard Pointing devices Touch screens Pen input Motion input Voice input Video input Scanners and reading devices Keyboards Keyboards Dome Switch Keyboards Mechanical Keyboards Aka ‘membrane keyboard’ Uses a thin rubber or silicon Uses individual switches layer with individual domes per key per key that collapse when More expensive pressed More tactile because keys Relatively quiet and low cost can register even if Can fail to register keystrokes pressed halfway when not pressed down far enough Keyboards Pointing Devices Pointing Devices Trackballs – essentially are upside down mechanical mice Touchscreens Capacitive Touchscreens Resistive Touchscreens Rely on conductivity of objects to sense their Made up of several layers, the topmost of location on the screen which relies on pressure to sense the location of objects Generally considered more sensitive and responsive compared to resistive screens Generally considered more accurate compared to capacitive screens Pen Inputs Motion Input Audio Input Voice Input Image Input Mark Sensors and Code Scanners Magnetic Scanners Optical Scanners Optical scanner generates bitmap representations of printed images. A white light shines on the page or other flat surface Reflected light is detected by an array of photosensors that interpret the color on the scanned image Optical Character Recognition (OCR) uses a special-purpose processor or software to interpret bitmap content and search for patterns similar to printed characters Output Devices What Is Output? Text Graphics Video Audio Displays Displays Alternative Displays  Printers A printer is an output device that produces text and graphics on a physical medium Impact Printers make contact with the printing medium to produce text A dot matrix printer moves a matrix of pins to press a ribbon soaked with ink over the paper. Commonly still used for high- speed printing of multicopy forms Printers Printers Printers Printers Printers Audio Devices Assistive Technologies Concepts in I/O Devices I/O Operations and Data Transfer (1/3) I/O Operations and Data Transfer (2/3) I/O Operations and Data Transfer (3/3) Device Drivers (1/5) Device Drivers (2/5) Device Drivers (3/5) Device Drivers (4/5) Device Drivers (5/5) Buffering in I/O Devices Buffering is the temporary storage of data while it is being transferred between devices or processes that operate at different speeds. Role in I/O: Buffers allow the CPU to continue other tasks while data is processed by slower devices (e.g., printers, hard drives). Buffers smooth out differences in data transfer rates, preventing bottlenecks. Examples: Printing: Data is sent to a buffer (spooler) while waiting for the printer to process it at its own pace. Video Streaming: Data is buffered in advance to ensure smooth playback even with minor network fluctuations. Caching in I/O Devices Caching is the process of storing frequently accessed data in a faster storage medium (e.g., RAM) for quicker retrieval. Role in I/O: Caching improves efficiency by reducing the need to fetch data from slower storage (e.g., hard drives) repeatedly. It reduces access time for data that is frequently requested, speeding up I/O operations. Examples: CPU Cache: Stores frequently accessed instructions and data, allowing the CPU to quickly retrieve them, improving overall system performance. Web Browser Cache: Stores web page elements like images and scripts, speeding up page load times for future visits. Addressing and Virtualization (1/3) How devices are addressed in a system Addressing and Virtualization (2/3) Concept of virtualization in I/O devices In virtualized environments, physical I/O devices are emulated as virtual devices. These virtual devices allow multiple virtual machines (VMs) to share the same physical hardware without direct access to it. The virtualization layer (hypervisor) manages the communication between virtual machines and the physical I/O devices, allowing each VM to interact with devices as if they have dedicated access. This helps optimize hardware usage and provides flexibility, especially in cloud environments where resources are shared. Addressing and Virtualization (3/3) Use cases for virtual devices in modern systems Cloud Environments: Virtual devices are common in cloud services where multiple virtual machines need to share hardware resources. For example, in a cloud data center, multiple VMs can share a single physical network interface card (NIC) through virtual NICs, ensuring efficient use of hardware. Development and Testing: Virtual devices are often used by developers to simulate hardware for testing purposes without needing the actual physical device. For instance, virtual network interfaces can be used to test software designed for specific network hardware configurations Performance Considerations in I/O (1/3) Data Transfer Rate: This is the speed at which data moves between the I/O device and the system (usually measured in MB/s or GB/s). Higher transfer rates mean data can be processed more quickly. Example: A solid-state drive (SSD) typically has a faster data transfer rate than a traditional hard drive (HDD), which means data can be read and written faster. Latency: Latency is the time delay between the moment a request is made and the time the data begins to be transferred. Lower latency means faster response times. Example: In a high-performance computing (HPC) environment, low latency is crucial, especially for tasks like video rendering, where quick data access is required. Bandwidth: Bandwidth refers to the maximum amount of data that can be transferred at a given time. High bandwidth allows more data to be transferred simultaneously, which is particularly important for applications that deal with large volumes of data. Example: Servers that handle large datasets or multiple users benefit from high bandwidth to avoid slowdowns during data-heavy operations. Performance Considerations in I/O (2/3) Importance of Efficient I/O in High Performance Computing (HPC) Environments In HPC environments—such as data centers, servers, or workstations used for tasks like video editing or scientific simulations—efficient I/O is crucial. Poor I/O performance can create bottlenecks, where the CPU or memory is waiting for data from slower I/O devices, which slows down the entire system. For example, in video rendering or database management, where large volumes of data need to be processed quickly, inefficient I/O can significantly reduce productivity. Performance Considerations in I/O (3/3) Direct Memory Access (DMA): Reducing Context Switching: Efficient Use of Buffers and Caches: