Year 11 CPU architecture

• Computing
• Upper Secondary (Key Stage 4)
• Lower Secondary (Key Stage 3)

Year 11 Computer architecture

Log into your student accounts and go to the following website

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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.

What is the MAR?

What is RAM?

What are the data types?

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

Learning intension

By the end of this lesson will understand how what affects the CPU performance.

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​.

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 different ‘levels’ of cache:​

• Level 1 cache is extremely fast but small (between 2-256KB), located on the CPU. Each core will have its own level 1 cache​.
• Level 2 cache is usually also given to each core. It is very fast, but a little slower than level 1 cache. The typical size is 256KB-8MB​.
• Level 3 cache is the slowest type of cache, but still faster than RAM. It is usually located on the CPU and stores ​4MB-50MB. The cache is shared between all the cores on ​the processor.​

The data used most often by the CPU is held in ​Level 1 cache so is available extremely quickly​.

In most systems, Level 1 cache is used about 50% of the time, with Level 2 cache being accessed about 90% of the time.​

This greatly reduces the time that the CPU has to wait for data from main memory​.

The size of the Level 2 cache is a major factor in determining the performance of the CPU​.

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​.

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

• Cache
• Cores
• Clock speed

The three C's

Clock speed

Everything in a computer happens on the pulse of

the internal clock​

Therefore, the faster the clock speed, the faster the

instructions are processed​

• One cycle per second = 1 hertz (Hz) = 1 instruction carried out each second​
• 1 kilohertz (kHz) = 1000 cycles per second​
  
• 1 Megahertz (MHz) = 1,000,000 cycles per second​
  
• 1 Gigahertz (GHz) = 1,000,000,000 cycles per second​
  

Look up the system information of your pc. 

How fast is your computer’s processor?​

Remember, a 1 GHz processor is performing one billion

cycles per second​

• A dual-core processor has two processors in the same integrated circuit, linked together​.

• A dual-core processor has the potential to perform two instructions at the same time​.

• This allows twice as many instructions to be executed, however, it doesn’t always perform at this rate as software may not be able to take full advantage of both cores​.

• A quad-core processor has four linked processors.​

Which processor would you prefer, a dual-core 1GHz, or a
3GHz single core processor?

forms.office.com

What are the three c's?

Which is theoretically faster?

1. Dual core 4ghz
2. Quad core 1ghz
3. Single core 8ghz
4. Quad core 3ghz