The system unit of a computer system

System Unit

Peripherals

storage peripheral

communication peripheral

output peripheral

input peripheral

mouse

microphone

keyboard

speaker

printer

USB flash drive

broadband modem

components

connected by

system bus

address buses

control buses

data buses

Display card

hard disk

Power supply

DVD-ROM drive

motherboard

floppy disk drive

Memory

CPU

Transfer data and instructions.

Transfer the source address or the destination address of data.

Indicate the direction of the data transfer and coordinate the
timing of the event during transfer.

main memroy

Cache memory

Random Access Memory (RAM)

Read-only memory (ROM)

functions

with attributes

executes machine cycle

contains

word length

clock rate

sub-cycles

execute

decode

interrupt

fetch

registers

control unit (CU)

Arithmetic and logic unit (ALU)

control register (CR)

General purpose register (GPR)

Use registers to hold data during calculations

Results are usually stored in a register called an accumulator

Perform arithmetic and logical operations

Keep track of the sequence of instructions being processed

Monitors and coordinates all I/O operations and system units

functions


Provide storage space for ALU and CU.

Fastest way for a CPU to access data

Memory units inside a CPU

types

Counter (CX)

Data register (DX)

Base register (BX)

Accumulator (AX)

functions

Load data from main memory into a register.

Store data temporarily in arithmetic operations.

Store data from a register into main memory.

functions

Contain the instructions to be executed by the CPUs

Contains the memory address of the next instruction to be executed

Facilitate the communication of the CPU with the main memory through the system bus.

types

Instruction Register (IR)

Program Counter (PC)

Memory Address Register (MAR)

Memory Data Register (MDR)

Status registers

Contain a number of flag bits indicating the status after the execution of instructions

Used in instructions of conditional testing and program branching

Read the next instruction from the main memory into instruction register (IR).

Identify the operation code and operands in an instruction.

Interpret the operation code and perform the required operation.

end of the execution of an instruction

Measure speed of CPU

Number of bits of data and instructions can handle at one time.

volatile

non-volatile

types

Erasable programmable read-only memory (EPROM)

Electrically erasable programmable read-only memory (EEPROM)

store the permanent information suppliesd by the manufacturer

contain the bootstrap program which loads and initializes the operation system of the computer

function

temporiy hold the data and instructions of application software and the operations system

types

Static Random Access Memory (SRAM)

Dynamic Randonm Access memory (DRAM)

high-speed memory

store data and instructions that have been recently used by the CPU

latest development of CPU and main momery

parallel processing of multiple cores

better pipeline technology

smaller chip die

high speed Double-Date Rate 3 (DDR3)SDRAM

shortern the speed gap between the CPU and main memory

operates a lower voltage level but higher frequency than its processsor