The System Unit

The System Unit

1. System Unit

   • System Chassis
     • Container that houses most of the electronic components that make up a computer system
   • System Unit
     • Contains system's electronic components and selected secondary storage devices

2. System Unit Types

   • Laptops
   • Smartphone
   • Desktops
   • Waearables
   • Tablets

3. Components

   • Memory
     • Volatile memory (loses its content when power is turned off)
       • Random Access Memory (RAM) - chips hold program and data that the CPU is presently processing
       • Cache memory - temporary, high-speed holding area between the memory and CPU
       • Virtual memory- a memory management capabilities that uses hardware & software to allow a computer to compensate for physical memory shortages from RAM to disk storage
     • Non volatile memory (does not lose contents when power is removed)
       • Read-only memory (ROM) - information stored by the manufacturer. contain special instructions
       • Flash memory - combines of the features of RAM and ROM, contains startup infromation
   • Microprocessor
     • Two Basic Components of the CPU:
       • Control unit - tells the computer system how to carry out a program's instruction
       • Arithmetic-logic unit (ALU) - performs arithmetic and logical operations
     • Specialty Processors
       • Coprocessors - designed to improve specific computing operations
         • Designed to handle a variety of specialized tasks (3D images, encrypting data, etc)
     • Multicore Chips
       • Multicore Processors - Two or more separate and independent CPUs within a system unit
       • Parallel Processing - Computer's ability to divide tasks into parts that can be distributed across each core
   • System board
     • System board/main board/motherboard controls communication for the entire computer system
     • Sockets & Chips
       • Sockets - the connection point for chips
       • Chips - tiny circuit boards etched onto squares of silicon
     • Slots & Bus Lines
       • Slots - provide a connection point for specialized cards/ circuit boards & provide expansion capabilities for the computer
       • Bus Lines - Connecting lines that provide pathways to support communication among electronic components

4. Expansion Slots & Cards

   • graphic cards - for high quality 3D graphics
   • Network Interface Cards (NIC) - connect devices to networks via cables
   • SD cards - expansion cards for mobile devices

5. Bus Lines/Bus/Expansion Buses

   • connect parts of the CPU to each other and various other components on the system board
   • Sysytem bus/ Expansion bus
   • USB, FireWire and PCI Express (PCIe)

6. Ports

   • sockets for connecting external devices to the system unit. Ports connect directly to the system board, to cards inserted into slots on the system board
   • -USB, Ethernet, HDMI, Thunderbolt
   • eSATA, MIDI, MiniDP, VGA & DVI

7. Cables

   • Used to connect external devices to the system units via the ports.
   • One end of the cable is attached to the device and the other end has a connector that is attached to a matching connector on the pot

8. Power supply

   • Computers require direct current(DC) power converting alternating current (AC) from wall outlets or batteries

9. Numeric Representation

   • two -state binary system consists of only two digits called bits (on= 1; negative charge, off= 0; no charge
   • Hexadecimal system
     • Uses 16 digits to represent binary numbers

10. Character Encoding

    • ASCII, EBCDIC, Unicode