The System Unit
- It is a case that contains electronic components of the computer used to process data- It includes:
- Drive bay(s), aka DVD driver
- Power supply
- Sound card
- Video card
- Processor, aka CPU
- Memory
- Motherboard is the main circuit board
- A computer chip contains integrated circuit
Processor
- Central Processing Unit (CPU) interprets and carries out the basic instructions that operate a computer- CPU contain a Control Unit (CU) & Arithmetic Logic Unit (ALU)
- Types of processor:
- Multi-core processor
- Dual-core processor
- Quad-core processor
- How processor works with other computer components
- Arithmetic Logic Unit (ALU) performs arithmetic, comparison and other operations
- A processor repeats a set of 4 basic operations for every instruction
1. Fetch
2. Decode
3. Execute
4. Store
- The operations comprise a machine cycle
- Pipelining means processor begins fetching a second instruction before it completes the machine cycle for the first instruction
- System clock controls the timing of all computer operations
- Clock speed is the pace of the system clock, and is measured in Gigahertz (GHz)
- Intel & AMD are the leading manufacturers of personal computer processor chip
- Cooling system for processor chip:
- Heat sinks
- Liquid cooling technology
- Parallel processing uses multiple processors simultaneously to execute a single program or task
Data Representation
- Analog signal are continuous and vary in strength & quality- Digital signals are in one of two states: on/off
- Most computers are digital
- The binary system uses two unique digits (0 & 1)
- A computer circuit represents the 0 & 1 electronically by the presence or absence of an electrical charge
- 8 bits = 1 byte
- A byte represents a single character (alphabet, number, symbol) in the computer
- American Standard Code for Information Interchange (ASCII) is the most widely used coding scheme to represent data
Memory
- It consists of electronic components that:- Store instructions waiting to be executed by the processor
- Store data needed by those instructions
- Store the result of processing the data
- It also stores 3 basic categories of items:
- Operating system & system software
- Application programs
- Data being processed and the resulting information
- Each location in memory has an address
- Memory size is measured in Kilobytes (KB), Megabytes (MB), Gigabytes (GB) or Terabytes (TB)
- There are 2 types of memory:
- Volatile memory - Loses its contents when power is turned off. Eg: Random access memory (RAM)
- Non-volatile memory - Does not lose contents when power is removed. Eg: Read-only memory (ROM), flash memory & CMOS
- 3 basic types of RAM chips:
- Dynamic RAM (DRAM)
- Static RAM (SRAM)
- Magnetoresistive RAM (MRAM)
- Amount of RAM required:
ROM
- Memory chips storing permanent data & instructions (Eg: firmware)
- Programmable read-only memory (PROM) chip is a blank ROM chip that can be written to permanently
- Electrically erasable programmable read-only memory (EEPROM) can be erased
- Flash memory can be erased electronically and rewritten
- CMOS technology provides high speeds and consumes little power
Access Time
- It is the amount of time it takes the processor to read from memory, measured in nanoseconds
Expansion Slots and Adapter Cards
- An expansion slots is a socket on the motherboard that can hold an adapter- An adapter card enhances functions of a component of the system unit and/or provides connections to peripheral device (monitor, mouse/keyboard, microphone, speaker)
- Removable flash memory includes:
- Memory cards
- USB flash drives
- PC cards/Express card modules
Ports and Connectors
- A port, aka jack, is the point at which a peripheral attaches to or communicates with a system unit- A connector joins a cable to a port
- Ports in a system unit
- Multiple peripherals can be connected using a single USB port
- Firewire port
- Bluetooth port (via serial/USB port)
- Small computer system interface (SCSI) port
- External serial ATA (eSATA) port
- Infrared Data Association (IrDA) port (via USB port)
- Serial port
- Musical Instrument Digital Interface (MIDI) port
- A smartphone might communicate with a notebook computer using an IrDA port
- A port replicator is an external device that provides connections to peripherals through ports built into the device
- A docking station is an external device that attaches to a mobile computer or device
Buses
- A bus allows the various devices both inside and outside attached to the system unit to communicate with each other- Types of bus:
- Data bus - carry data
- Address bus - carry address
- Expansion slots connect to expansion buses
- Common types of expansion buses:
- Peripheral Component Interconnect (PCI) bus
- PCI express bus
- Accelerated graphics port
- USB & firewire bus
- PC card bus
Bays
- A bay is an opening inside the system unit in which you can install additional equipment
Power Supply
- Power supply convert the wall outlet AC power into DC power- Some external peripherals have AC adapter, which is an external power supply. Eg: printer
Keeping Your Computer or Mobile Device Clean
- Clean your computer or mobile device once or twice a year- Turn off and unplug your computer or mobile device before cleaning it
- Use compressed air to blow away dust
- Use an antistatic wipe to clean the exterior of the case and a cleaning solution and soft cloth to clean the screen
Nice~
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