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1.1 systems architecture,

1.1 systems architecture

1.1 Architecture of the cpu

purpose of the cpu

The role of the CPU is to control the whole system it also decodes instructions and manages data it also communicates with other components in the system.

the FDE cycle

fetch= an instruction is fetch from main memory
decode= the instruction are decoded in the control unit
execute= to run the instruction

components of the cpu

the arithmetic logic unit=

Carries out logical operations such as AND,OR and NOT

Shift operations –the bits in a Computer word can be shifted left and right

Arithmetic Operations such as addition, subtraction, multiplication and division

control unit =

Controls the execution of instructions in the correct sequence

Decodes instructions

Regulates and controls processor timing using pulses from the system clock

Send and receives control signals to and from other devices in the3 system

cache=

Fast but small memory
Stores frequently used instructions or data e.g. variables that are being used in a loop

registers of the cpu

register=A register is a very small fast acting memory storage. they are volatile. holds memory addresses and data

program counter=Holds the memory address of the next instruction to be processed

memory address register Holds the memory address of the instruction or data to be fetched
The MAR is directly connected to the main memory but ti can only go in one direction

accumulator=

Special purpose register

Directly connected to the ALU

Stores the result of operations completed in the ALU

memory data register=Holds the data or instruction temporarily after it has been fetched from the main memory
The MDR is directly connected to the main memory, data and instructions can go to and from main memory

1.2 Factors affecting CPU performance

cache size
Stores frequently used pieces of information, but can only read data from top to bottom meaning it becomes less efficient the bigger it is

number of cores

The more cores there are the more instructions can be executed at the same time

A core is a single processor

Most cpus are now multi core processors

Allow for parallel

clock speed

Measured in hertz

Number of cycles per second

Modern processors run at around 3GHz

he higher the clock speed the more FDE cycles can be carried out in a time

One common bottleneck is the access of the main memory

1.3 Embedded Systems

An embedded system is a computer that is built into another piece of equipment designed to have a specific function.

Embedded systems include things such as cameras, aircraft, vending machines, microwaves, ovens, fridges or sat navs. Most electronic devices will contain a microprocessor that can be considered as an embedded system.

Embedded systems are usually employed where a task is simple but needs to be reliable to control a limited range of resources such as timers or actuators.

The programs are held in Read Only Memory (ROM) it cannot be easily changed although some devices do allow for firmware updates to be performed. An embedded system executes programs that are written specifically for the tasks and these programs are written to use the least possible memory and for them to execute as quickly as possible.

There is a limited operating system that does not need loading when a device is turned on as it is all stored in ROM, this operating systems will only be able to run a single application.

As with all computer systems there is likely to be a user interface for example a microwave or washing machine has buttons although some will have no interface at all.

Other embedded systems might rely on gathering information from the environment such as central heating system that reacts to time and temperature.