1. Lesson 2: Elements of a Personal Computer
• System unit
• Microprocessor chip
• How memory is measured
• What ROM is
• What RAM is
• How memory works
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2. 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
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3. The Microprocessor Chip
Processor (CPU) MHz or GHz
8088 (XT) 4 to 10 MHz
80286 (286 or AT) 8 to 16 MHz
80386SX/DX (386SX/DX) 16 to 33 MHz
80486 (486) 25 to 100 MHz
Pentium 60 to 200 MHz
6x86 120 to 166 MHz
Pentium (MMX) 166 to 200 MHz
Pentium PRO 150 to 200 MHz
Pentium II 200 to 400 MHz
Pentium III 500 MHz to 1.2 GHz
Pentium 4 or Pentium M 1.4 to 3.2+ GHz
Pentium 5 5 GHz to 7 GHz
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4. 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 Bytes
1 Megabyte = 1,048,576 Bytes
1 Gigabyte = 1,073,741,824 Bytes
1 Terabyte = 1,099,511,627,776 Bytes
1 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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5. 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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6. 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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7. Random Access Memory (RAM)
Processor (CPU) MHz / GHz Typical RAM
8088 (XT) 4 to 10 640Kb
80286 (286 or AT) 8 to 16 1 to 2Mb
80386SX/DX (386SX/DX) 16 to 33 1 to 8Mb
80486 (486) 25 to 100 4 to 32Mb
Pentium 60 to 200 8Mb plus
6x86 120 to 166 16Mb plus
Pentium (MMX) 166 to 200 16 to 32Mb
Pentium PRO 150 to 200 32Mb plus
Pentium II 200 to 400 32Mb plus
Pentium III 500 to 1.2 64Mb plus
Pentium 4 1.4 to 2.2 128Mb plus
Pentium 5 5 to 7 256Mb plus
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8. Understanding How Memory Works
1. 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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9. Lesson Summary
• System unit
• Microprocessor chip
• How memory is measured
• What ROM is
• What RAM is
• How memory works
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