MBMPowered by DeSiaMore System Unit 1

MBMPowered by DeSiaMore Definition The system unit/system cabinet is a container that houses most of the electronic components that make up the computer system. Types of the system units vary depending on the type of the microcomputer e.g. Desktop, Notebook, and Tablet system units. 2

MBMPowered by DeSiaMore System unit components  Motherboard/Mainboard  CPU  Memory  Bus lines  Ports and Cables  Power Supply  System Clock  Expansion Slots 3

MBMPowered by DeSiaMore Motherboard Board  Also known as main board or system board  Allows I/O devices to communicate with the system unit.  It provides connections between processors, memory units, and sockets or expansion slots.  A flat circuit board with sockets and chips 4

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MBMPowered by DeSiaMore Expansion Slots  Expansion slots are where additional circuit boards can be plugged in.  Each expansion slot has 1 external port where a peripheral device can be connected. 7

MBMPowered by DeSiaMore Microprocessor  CPU control unit arithmetic and logic unit Registers – Instruction register Data register 8

MBMPowered by DeSiaMore Control Unit  Tells system how to carry out program instructions  Directs flow between memory and the arithmetic and logic unit  Directs signal flow between the CPU and input and output devices 9

MBMPowered by DeSiaMore Arithmetic Logical Unit (ALU)  performs arithmetic and logical operations on data adds, subtracts, multiplies, compares 10

MBMPowered by DeSiaMore Registers Special-purpose High-speed Temporary storage Located inside CPU Instruction register Holds instruction currently being executed Data register Holds data waiting to be processed Holds results from processing 11

MBMPowered by DeSiaMore Microprocessor Chips  Word size Number of processed bits at a time Expresses chip capacity Size of word determines power 12

MBMPowered by DeSiaMore Memory  Computer memory is a collection of chips on the motherboard where all computer processing and program instructions are stored while in use.  It enables the CPU to retrieve data quickly for processing. 13

MBMPowered by DeSiaMore Memory Capacity Kilobyte (KB) 1,000 bytes Gigabyte (GB) 1 billion bytes U U n n i i t t C C a a p p a a c c i i t t y y Megabyte (MB) 1 million bytes Terabyte (TB) 1 trillion bytes 14

MBMPowered by DeSiaMore Types of Memory  RAM-Random access Memory- also known as main memory or primary memory  ROM – read only memory  CMOS-Complementary Metal- oxide semiconductor. 15

MBMPowered by DeSiaMore  holds data and programs being processed by CPU  Volatile - when power shuts off, contents of RAM are emptied  Exception - flash RAM can retain data when power disrupted, used in high end portable computers RAM 16

MBMPowered by DeSiaMore ROM  Read-only memory Also called Firmware Cannot be changed by the user Used for start-up instructions, keyboard control capabilities 17

MBMPowered by DeSiaMore CMOS Complementary metal-oxide semiconductor:  Flexible and expandable memory  Holds startup information on system components  Non-volatile  Its contents may be updated 18

MBMPowered by DeSiaMore Bus Lines  Data pathways that connect system components  Data roadway for traveling bits  More lanes, faster traffic; 64 bit bus faster than a 32 bit 19

MBMPowered by DeSiaMore Ports and Cables  Ports are connecting sockets  Cables connect input and output devices to ports 20

MBMPowered by DeSiaMore System Clock  Is a circuit that emits a continuous stream of high and low pulses that are all exactly the same length  Controls speed and synchronizes operations  Expressed in megahertz  Determines the speed of the computer 21

MBMPowered by DeSiaMore System boardHolds the various other system components Microprocessor Contains the CPU on a chip MemoryHolds programs and instructions System clock Controls speed of computer operations Expansion Connect to network and other slots/boardssystem capabilities Bus lines Connect various internal system components PortsConnect outside devices to system unit ComponentFunction SUMMARY OF THE SYSTEM UNIT COMPONENTS 22

MBMPowered by DeSiaMore How does the computer process data? A computer is an information-processing machine that works by converting all kinds of data/information into binary numbers (ones and zeros) and then using simple mathematics to make decisions about, or to rearrange, those numbers 23

MBMPowered by DeSiaMore How does the computer process data?  Data and instructions are represented in a binary form  In binary form, ones, can be stored as magnetized spots while the zeroes can be stored as unmagnetized spots on a hard disc.  Movement and transformation of electrical pulses in electrical circuits. 24

MBMPowered by DeSiaMore Data Representation  Binary.i.e Os and 1s  Bit: BInary digiT Smallest unit of information/storage - sufficient to hold one bit Can take one of two values (true and false or 0 and 1, or yes or no)  Byte: Smallest addressable unit of storage Usually 8 bits Typically holds one character 25

MBMPowered by DeSiaMore Word –Fundamental unit of storage in a computer –Word size is one of chief distinguishing characteristics of a computer –Typical size in modern computers: 4 bytes or 8 bytes –An instruction is usually one or more words long –A word can be used to hold a whole number of characters 26

MBMPowered by DeSiaMore Data Data: Numbers, characters, images, or other method of recording Represented in binary. Has no meaning on its own. When interpreted by data processing system it takes on meaning and becomes information. Data storage: –Setting of individual bits to specific values, destroying its previous contents Data retrieval: –Copying the contents of a particular memory cell to another storage area. –Original data remains unchanged 27

MBMPowered by DeSiaMore Binary Coding Schemes  ASCII – used for microcomputers  EBCDIC – used for large computers  Unicode – 16 bit code Used to support International Languages 28

MBMPowered by DeSiaMore How the letter is represented in ASCII code. Binary Coding Schemes 29

MBMPowered by DeSiaMore ASCII code 30

MBMPowered by DeSiaMore Machine Cycle  A machine cycle is a series of steps a CPU takes to execute an instruction Instruction Cycle  Fetching- for command or data  Decoding – break down the command to resemble those in the CPU’s instruction set. Execution Cycle  required data located  instruction executed  results stored 31

MBMPowered by DeSiaMore How fast is a computer?  Cycle Time Measured in MIPS – millions of instructions per second (also known as Megahertz) slow (milliseconds) medium (nanoseconds) fast (picoseconds) 32

MBMPowered by DeSiaMore Microprocessor Technology and Speed Affected by size of word (size of registers)  how many bits the processor can read Affected by width of bus  How many bits can travel along the bus Affected by Clock Speed Reduced Instruction Set Computing (RISC) 33