Chapter 4

 CHAPTER 4 : System unit components
The System Unit:
System unit is a case that contains electronic components of the computer used to process data.
The inside of the system unit on a desktop for personal computer includes:

• Drive Bay(s)
• Power Supply
• Sound Card
• Video Card
• Processor
• Memory

Motherboard is the main circuit board of the sustem unit.

Processor where it is also called as the Central processing unit (CPU), interprets and carries out the basic instructions that operate a computer and contain a control unit and an arithmetic logic unit (ALU).

There are three type of core processor:-

• MULTI-CORE PROCESSOR
• DUAL-CORE PROCESSOR
• QUAD-CORE PROCESSOR

Four basic operation cycle:-

• FETCH
• DECODE
• EXECUTE
• STORE

Control unit is the component od the processoe that directs and coordinates most of the operations in the computer.

Arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations. 

The processor contains registers, that temporarily hold data and instructions. The System clock controls the timing of all computer operations where system clock is measured in Gigahertz (GHz).

Data representation

Analog singals are continuous and vary in strength and quality.

Digital singals are in one of two states;on or off

Binary system uses two unique digits (0 and 1)

-Bits and Bytes

A computer circuit represents the 0 and 1 electronically by the presence or absence of an electrical charge. Eight bits grouped together as a unit are called a byte. A byte represents a single character in the computer.

MEMORY:

Memory consists of electronic components that store instructions and data that from the computer system unit.

Two type of memory that used commonly:-

-Nonvolatile memory - does not lose or delete the content when power is off such as ROM, FLASH MEMORY and more.

-volatile memory - loses its content when power is turn off.

Process of program instruction transfer in and out of RAM

Type of RAM chips:

• Dynamic RAM (DRAM)- SDRAM,DDR SDRAM, RDRAM
• Static RAM (SRAM)
• Magnetoresistive RAM (MRAM)

-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.
-A PROM is programmable read only memory chip is a blank ROM chip that can be written to permanently and EEPROM is that can be erased.
-Flash memory can be erased electronically and rewritten.

Ports and connectors:-
A port is the point at which a peripheral attaches to or communicates with a system unit where connector joins a cable to a port.

 A USB port can connect up to 127 different peripherals together with a single connector 

Other types of ports include:-

• Firewire port
• Bluetooth port
• SCSI port
• eSARA port
• IrDA port
• Serial port
• MIDI port

BUSES:-

A bus allows the various device both inside and attached to the system unit to communicate with each other. There are two type of bus, Data bus and Address bus.

Common types of expansion buses include:-

• PCI bus
• PCI Express bus
• Accelerated Graphics port
• USB Firewire bus
• PC card bus

- A bay is an opening inside the system unit in which you can install additional equipment.