Components of System Units

• The motherboard is the main circuit board of the system unit
• Components inside the system unit on a desktop personal computer

  • Drive bay
  • Power supply
  • Sound card
  • Video card
  • Processor
  • Memory
• The system unit is a case that contains electronic components of the computer used to process data
• For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle
• The control unit is the component of the processor that directs and coordinates most of the operations in the computer
• The arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations
• The processor contains registers, that temporarily hold data and instructions
• The processor, also called the central processing unit (CPU), interprets and carries out the basic instructions that operate a computer
• The leading manufacturers of personal computer processor chips are Intel and AMD
• The system clock controls the timing of all computer operations
• Determine how you plan to use a new computer before selecting a processor
• Cooling methods for processor chips

  • Heat sinks
  • Liquid cooling technology
• A processor chip generates heat that could cause the chip to burn up
• The data bus moves data to and from primary storage
• The address bus transmits signals for locating a given address in primary storage
• Additional cooling is required for processors
• The control bus transmits signals specifying whether to "read" or "write" data to or from a given primary storage address, input device, or output device
• Three types of buses link the CPU, primary storage, and other devices in the computer system
• A bus is a channel through which data are passed in electronic form
• A computer circuit represents the 0 or the 1 electronically by the presence or absence of an electrical charge
• Analog signals are continuous and vary in strength and quality
• Bits and bytes are used in the binary system
• Most computers/devices nowadays are digital
• The binary system uses two unique digits (0 and 1)
• Digital signals are in one of two states: on or off
• The capacity of a bus, called bus width, is defined by the number of bits they carry at one time
• Memory size is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB)
• Each location in memory has an address
• Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data
• Three basic categories of items stored in memory

  • The operating system and other system software
  • Application programs
  • Data being processed and the resulting information
• Eight bits grouped together as a unit are called a byte, representing a single character in the computer
• The system unit contains two types of memory: Volatile memory and Nonvolatile memory
• The amount of RAM necessary in a computer often depends on the types of software you plan to use
• Examples of Volatile memory


  • RAM
• Examples of Nonvolatile memory

  • ROM
  • Flash memory
  • CMOS
• RAM chips usually reside on a memory module and are inserted into memory slots
• Memory cache speeds the processes of the computer because it stores frequently used instructions and data
• Read-only memory (ROM) refers to memory chips storing permanent data and instructions
• Firmware is stored in ROM
• A PROM (programmable read-only memory) chip is a blank ROM chip that can be written to permanently