Flashcards · 0478 · Topic 3

Hardware flashcards

24 cards on Topic 3, subtopics 3.1 to 3.4. Pick a subtopic or study them all.

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3.1 Computer architecture

What do the ALU and the CU do?: ALU (arithmetic logic unit): carries out arithmetic and logic operations. CU (control unit): sends control signals that manage the fetch-decode-execute cycle and the flow of data in the CPU.
What do the PC, MAR, MDR, CIR and ACC hold?: PC: address of the next instruction. MAR: address being accessed in memory. MDR: data or instruction being moved to or from memory. CIR: instruction being decoded and executed. ACC: result of ALU operations.
What do the address bus, data bus and control bus carry?: Address bus: memory addresses (where), one way from the CPU. Data bus: data and instructions (what), both ways. Control bus: control signals such as read, write and clock, both ways.
Describe the fetch stage of the fetch-decode-execute cycle: The address in the PC is copied to the MAR. The instruction at that address is copied from RAM to the MDR, then to the CIR. The PC is incremented to point to the next instruction.
How do cores, cache and clock speed affect CPU performance?: More cores: more instructions processed at once. Larger cache: more frequently used data held close to the CPU, so fewer slow trips to RAM. Faster clock: more cycles, so more instructions, per second.
What is an instruction set?: The list of all the commands, in machine code, that a particular CPU can process.
What is an embedded system?: A computer system built into a larger device to perform one dedicated function, e.g. in a washing machine, car, security system or vending machine. A PC, by contrast, is general-purpose.

3.2 Input and output devices

Name six input devices on the 0478 syllabus: Any six of: barcode scanner, digital camera, keyboard, microphone, optical mouse, QR code scanner, touch screen (resistive, capacitive or infra-red), 2D scanner, 3D scanner.
Name six output devices on the 0478 syllabus: Any six of: actuator, DLP projector, LCD projector, inkjet printer, laser printer, LED screen, LCD screen, speaker, 3D printer.
What is a sensor?: An input device that measures a physical property of its surroundings (such as temperature, light or pressure) and sends the reading to a computer, usually as an analogue signal that is converted to digital.
Which sensor would you use to: detect an obstacle near a car; measure soil wetness; detect a gas leak?: Obstacle: proximity sensor (or acoustic sensor). Soil wetness: moisture sensor. Gas leak: gas sensor.
What is an actuator?: An output device that turns a signal from a computer into physical movement or action, e.g. a motor, pump, valve or heater.

3.3 Data storage

Primary vs secondary storage: Primary storage (RAM and ROM) is directly accessed by the CPU. Secondary storage (HDD, SSD, optical discs) is not directly accessed by the CPU, is non-volatile and is used to store data and programs long-term.
RAM vs ROM: RAM: volatile, read and write, holds the programs and data currently in use. ROM: non-volatile, read-only, holds the start-up (bootstrap) instructions.
How does magnetic storage (an HDD) store data?: Data is stored on spinning platters divided into tracks and sectors. A read/write head uses an electromagnet to magnetise areas of the surface, representing 1s and 0s.
How do optical and solid-state storage store data?: Optical (CD, DVD, Blu-ray): a laser burns and reads pits and lands on the disc surface. Solid-state (SSD, SD card, USB drive): NAND or NOR flash memory, using transistors with control gates and floating gates to trap charge.
What is virtual memory and why is it needed?: Part of secondary storage used as if it were RAM when RAM is full. Pages of data not currently needed are moved from RAM to virtual memory and back when needed, so more programs can run than RAM alone allows.
Give one advantage and one disadvantage of cloud storage compared with local storage: Advantage: data can be accessed from anywhere with an internet connection. Disadvantage: it relies on a network connection and on physical servers run by a third party.

3.4 Network hardware

What is a network interface card (NIC)?: The hardware a device needs to connect to a network. It is given a MAC address at manufacture.
What is a MAC address?: A unique address fixed to a device's NIC at manufacture, written in hexadecimal. It is made up of a manufacturer code and a serial code.
What is an IP address, and how does a static IP address differ from a dynamic one?: An address allocated by the network that identifies a device's location on it. A static IP address stays the same; a dynamic one is assigned each time the device connects and can change.
IPv4 vs IPv6: IPv4: 32 bits, written as four denary numbers 0-255 separated by dots. IPv6: 128 bits, written as eight groups of four hexadecimal digits separated by colons, allowing far more addresses.
What does a router do?: It sends data packets to a specific destination on a network, can assign IP addresses to devices, and connects a local network to the internet.
MAC address vs IP address: A MAC address is fixed at manufacture and identifies the network hardware itself. An IP address is allocated by the network, can change, and identifies where the device is on the network.