THE SYSTEM UNIT

 

SYSTEM UNIT

  

Type of system unit:

1. Desktop system units

2. Notebook system units

3. Tablet PC system units

4. Handheld computer system units



SYSTEM BOARD

System board also called the mother board. Function mother board is controls communications for the hold computer system.mother board using for all kind of different electronic components including

• sockets
• slots
• bus lines

Central Processing Unit (CPU).

 

• The CPU is the central electronic chip that determines the processing power of the computer.

                 

Does all of the work for the computer

1. Does all the mathematics, mainly addition.
2. Does all the logical comparisons of values.
3. Directs the flow of data in a computer.
4. Controls the operation of the parts of the computer.

Today, all CPUs are microprocessors.

1. A microprocessor is a complete computer on a silicon chip.
2. A microprocessor does all the function of the computer.   

• Stores data and informations waiting to be used.
• Follows changeable instructions.
• Does input, processing, and output

CPUs have three bacis parts.

• The Arithmetic Logic Unit (ALU).

        # Does all the nathematics in a computer.

        # Does all of the logic comparisons of values. 

• The Control Unit - directs the flow of information into the CPU and/or storage and controls which instructions the CPU will do next.
• Registers - used to store data and instructions inside the processor.

Speed of CPUs.

The speed of CPUs is measured in hertz.

• A hertz is on cycle per second.
• Need to measure time to determine cycles per second.
• Today, many CPUs can complete over six instructions per second.

Speed of modern CPUs.

• Most computers have a CPU that can do more than 400MHz.
• Computers will soon be at speeds of over a gigahertz, 1,000,000,000 Hertzs.

- MICROPROCESSOR

- SPECIAL PROCESSORS

• coprocessors

• smart cards

• specialty processors in car to control nearly everything from fuel efficiency to satellite entertainment and tracking systems.

• RFID tags

MEMORY

The function of memory is a holding rea for data, instruction, and information. memory has three type of memory chips :

• random-access memory (RAM)

1. Stores instructions that are used by the CPU
• Tells the CPU how to be the kind of computer it is, for example a Windows, Macintosh, or Play Station computers.
• Tells the CPU how to work with the different parts of the computer
• ROM can also hold programs that are directly accessed by the CPU.  One such program is the self-test when the computer is first turned on.  The self-test tests to seem if all the parts on the main circuit board (mother board) are working correctly.
2. The instructions in ROM can not usually be changed
• The instructions are built into the electronic circuits of the chips
• These instructions in ROM are called firmware
• To change the instructions in ROM you need to usually change the chips or do some other special process that is normally not available to an average user.
3. The instructions in ROM are nonvolatile.  They stay in ROM even when the computer is turned off.
4. Access to information is random access.
• Random access means that any piece of information in ROM can be accessed at any given time without access other information first.  It is a lot like the tracks on a music CD.  You can access any track at any time and in any order.
• The other kind of access is sequential access.  You must access the information in the order that they are located.  This is a lot like a music tape.  You must play the songs in order, or you have to fast forward past songs to get to the one you want.

•  read-only memory (ROM)

1. Store data and instructions that are used by the CPU to perform some task.
• These instructions are usually loaded into RAM from a secondary storage device.
• RAM is also used to store instructions that tell the CPU how to work with its parts.  These instructions are usually called drivers.
2. The instructions in RAM are constantly changing, depending on the needs of the CPU.
3. The instructions in RAM are volatile.
• When the computer is turned off the information in RAM disappears.
• The information in RAM needs to be saved to secondary storage before the computer is turned off.
4. Access to information is random access.

• FLASH MEMORY

EXPANSION SLOTS AND CARDS

Users can insert optional devices known as expansion cards into slots. include:

• grapics cards

• sound cards

• modem cards

• network interface cards (NIC)

• tv tuner cards

Sources:

1.  http://windows.microsoft.com/en-US/windows-vista/Parts-of-a-computer#section_6
2. http://dragon.ep.usm.edu/~it365/module/Basics/Basics.htm