Year 10 CPU architecture

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

Year 10 Computer architecture

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the code is written on the whiteboard.

Log into your student accounts and go to the following website

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the code is written on the whiteboard.

What is the MAR?

What is ROM?

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.

RAM – Random Access Memory

Holds data and instructions that are currently in use by the processor.

Located on the motherboard.

Directly accessible by the processor.

All data/instructions are lost once power is turned off.

ROM – Read Only Memory

Instructions are permanently etched onto a ROM Chip.

When power is turned off, instructions still remain on the ROM chip.

Bootstrap Loader is held in ROM.

Gives the instructions to start up the Operating System.

Why do you think RAM is erased?

Why do you think companies use ROM?

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​.

Memory type	Speed	Storage Capacity
Registers
Cache
RAM

Fast

Fastest

Small

Smallest

Large

Very Fast

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​.

Which of the following is NOT a function performed by the ALU?

1. Fetching instructions from memory
2. Adding two binary numbers together
3. Performing logical AND operations
4. Comparing if one number is greater than another

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

Data is passed between these CPU components using BUSES.

A bus is a set of parallel wires connecting two or more independent components of a computer system in order to pass signals between them.

There are 3 buses:

• Data bus
• Control bus
• Address bus

Address Bus

• Carries addresses from the processor to main memory or other I/O devices.
• It is one direction (uni-directional).
• The processor generates an address.
• All data/instructions are returned on the data bus.

Data Bus

• Carries data/instructions from main memory to the processor (or from other secondary storage devices) to the processor.
• Bi-directional (two way).
• Data can be read/written.

Control Bus

• Control signals are sent along the control bus
•  For example Memory Read and Memory Write
•  This instructs which was data will be travelling to/from memory.

Overview of the buses

I/O Devices

• Peripherals are any devices that are not directly connected to the CPU
  
• E.g. mouse, keyboard, printer, hard disk drive, CD-ROM drive.
  
• These devices are known as I/O devices (input/output devices).
  
• They connect using an IO port.

Secondary Storage

Used for long term storage of data and instructions:

• Hard disk drive
• Solid state drive
• Flash memory