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Lesson 2: Elements of a Personal Computer

• System unit

• Microprocessor chip

• How memory is measured

• What ROM is

• What RAM is

• How memory works

Looking at the System Unit • Often most important and expensive part

• Separate devices inside box perform specialized functions

• Notebook has same components as desktop

• Microprocessor chip− Often called “brain” of computer as instructions from

software programs and input received are executed here

− Referred to as Central Processing Unit (CPU) and processes information and instructions at different speeds

− Hertz (Hz) measures speed of internal computer clock in terms of frequency or number of cycles per second

− Dual and quad core processors contain two or four processor chips© CCI Learning Solutions Inc. 2

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The Microprocessor ChipProcessor (CPU) MHz or GHz8088 (XT) 4 to 10 MHz80286 (286 or AT) 8 to 16 MHz80386SX/DX (386SX/DX) 16 to 33 MHz80486 (486) 25 to 100 MHzPentium 60 to 200 MHz6x86 120 to 166 MHzPentium (MMX) 166 to 200 MHzPentium PRO 150 to 200 MHzPentium II 200 to 400 MHzPentium III 500 MHz to 1.2 GHzPentium 4 or Pentium M1.4 to 3.2+ GHzPentium 5 5 GHz to 7 GHz

Looking at Memory• Computers developed using numbering system of 1s and 0s or binary

system

• For computer to store information, must have memory chips installed

• Memory measured in bits and bytes− Bit is smallest unit of data used by computers

− Group of eight bits make one byte

1 Kilobyte = 1,024 Bytes1 Megabyte = 1,048,576 Bytes1 Gigabyte = 1,073,741,824 Bytes1 Terabyte = 1,099,511,627,776 Bytes1 Petabyte (PB) = 1,125,899,906,842,624 Bytes

• All data made up of bytes in combinations calculated by computer− Every file used in software program has specific file size

− Data file size increases or decreases based on contents stored

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Read Only Memory (ROM) BIOS• Group of integrated circuits responsible for:

− Starting computer

− Checking RAM

− Loading operating system

• Occurs only when computer first turned on or each time you restart (reboot) computer

• Reads information entered and processes it during time it resides in memory

− When process complete, clears itself and waits for next entry

− Does not perform any tasks other than reads information and

processes it

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Random Access Memory (RAM) • Located in system unit as electronic memory pool where

computer holds copies of programs and data

• Temporarily stores software program currently using and data created in program; may be referred to as system RAM

• RAM is volatile

• Measured in nano seconds (ns)

• Used in video display cards or to buffer information sent to printer

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Random Access Memory (RAM)Processor (CPU) MHz / GHz Typical RAM8088 (XT) 4 to 10 640Kb80286 (286 or AT) 8 to 16 1 to 2Mb80386SX/DX (386SX/DX) 16 to 33 1 to 8Mb80486 (486) 25 to 100 4 to 32MbPentium 60 to 200 8Mb plus6x86 120 to 166 16Mb plusPentium (MMX) 166 to 200 16 to 32MbPentium PRO 150 to 200 32Mb plusPentium II 200 to 400 32Mb plusPentium III 500 to 1.2 64Mb plusPentium 4 1.4 to 2.2 128Mb plusPentium 5 5 to 7 256Mb plus

Understanding How Memory Works1. ROM BIOS takes control when computer started and

loads operating system

2. When operating system gains control, see Windows “splash screen”

− Operating system checks Windows “registry,” which identifies what hardware and software installed

− When complete, see Windows “desktop”

3. Certain amount of RAM used to run basic files− As computer performs specific tasks, it uses RAM needed

− When starting software “application” or program, asking computer to put copy of program in RAM

− Close application program when not in use to make RAM available

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