Year 11 introduction

• Computing
• Upper Secondary (Key Stage 4)
• GCSE

Year 11 introduction

Log into your student accounts and go to the following website

www.lessonup.app

the code is written on the whiteboard.

Log into your student accounts and go to the following website

www.lessonup.app

the code is written on the whiteboard.

Who am I?

Who am I?

Over the course of the next year we will re-cover the following topics:

• System architecture
• Data representation
• Networks and protocols
• Boolean logic
• Programming

Two component papers, paper 1 is the theory paper and paper 2 logic and programming. Lessons will be split between the two. Programming will mainly be Fridays lessons.

What is a computer?

What is computer memory?

What is computer hardware?

Learning intension

By the end of this lesson you will recap your knowledge of CPU architecture.

The Central Processing Unit or CPU is arguably the most important component of a computer​

What does it do?​

What organ in the human body ​

is it often compared to?​

What are the similarities it has ​

to this organ?​

                         The CPU processes instructions​

• When you run a program, it is the ​CPU which runs the instructions​.
• It is often thought of as being ​the ‘brains’ of the computer​.
• The way that a brain works is ​very different to a CPU​.
• A CPU simply runs one ​simple instruction at a time​.
• It carries out billions of ​instructions per second​.

• Before about 1943, early computers stored the data to be worked on in memory.​
• The program was not stored.
• Instructions were input one at a time using switches, or read in punch cards and executed one at a time​.
• In 1943-44, mathematician von Neumann and his colleagues had the idea of storing the program instructions as well as the data in memory​.
• The stored-program computer was born!​

Essentially this means anything to do with a computer process is stored in the same box meaning memory.

The CPU accesses both instructions and data from the ​

same RAM.

The CPU has two major components 

• The​ Control Unit 
• Arithmetic-Logic Unit (ALU)​.

These connect to the memory unit inside of the CPU chip.

Inside the memory unit is registers and cache memory, these are used to carry out instructions. ​

• A register is a very fast ​memory location in the ​CPU.
• Cache is located on the CPU, it is slower to access than ​registers but faster than RAM​.

There are three logical operations what are they?

The ALU or Arithmetic Logic Unit is where the actual arithmetic operations are done​.

It also carries out logical operations such as those including AND, OR and NOT​.

CPU Registers

• Program Counter (PC) ​- holds the address of the next instruction to be executed​.
• Memory Address Register (MAR)​ - holds the memory address of the current instruction, and then the data that it uses, so that these can be fetched from memory​.
• Memory Data Register (MDR)​ - holds the actual instruction, and then the data that has been fetched from memory.​
• Accumulator​ (ACC) - holds the result of an instruction before it is transferred to memory​.

Von Neumann architecture uses the ‘stored program’ concept.
What does this mean?

Used for temporarily storing arithmetic and logic results. 

Points to the next instruction that needs to be executed. It is located in the Control Unit 

Used for holding the address of the

current instruction to be executed,

and the address of data to be used in instruction 

Used for holding the actual instruction or data that is stored in RAM. 

MAR

MDR

ACC

PC

Create a mindmap around the CPU architecture, what are features of registers? what are the registers, what is cache? what are the different levels of cache? what are the parts of the physical CPU? what is stored memory? what does the ALU do?

Control Unit - FDE cycle

The control unit coordinates and controls all of the activities taking place within ​the CPU.​

• It decodes instructions and executes them​.
• It receives signals from the system clock​.
• It directs the timing and control of other ​parts of the CPU, much like the conductor ​of an orchestra.​

• FETCH – causes the next instruction and any data involved to be fetched from main memory.​
• DECODE – decodes the instruction.​
  
• EXECUTE – the instruction ​is executed​.
• This process is then repeated…​