Section 1- systems architecture, memory and storage

• input - data from the real world that’s stored and processed to outputs in a computer

• Outputs

• Memory(primary storage) - holds or stores data/ programs/ operating systems currently being executed or in use

• Secondary storage

List and explain the basic models of a computer

He developed the concept of storage program computers, he used the idea data and programs can be stored in memory

Explain Von Neumann architecture

Is a hardware that executes programs and manages the rest of the hardware

What’s a CPU

A cache is a very fast memory that temporarily stores or holds data that will be needed by the processor during the course of running a program

What’s a cache

• decides instructions

• It’s controls and regulates processor timings using regular pulse from a system clock

• It’s sends and receives control signals to and from other devices within a computer

• It controls the execution of instructions in the correct sequence

Functions of the control unit

• cache

• ALU

• Registers

list what the processor consists of

Fetching the

Explain the fetch decode execute cycle

Registers are very fast memory located in the CPU used in the execution of instructions

What are registers

• MDR: they hold data or instruction temporarily when it is fetched or to be sent to main memory

• MAR: they store the memory address of the instructions to be fetched or stored by main memory

• PC (program counter): they hold the memory address of the next instruction to be processed

• Accumulator: they temporarily store the results of operations done in the ALU

List and explain the types of registers

• clock speed

• Cache size

• Number of cores

Factors that affects the CPU performance

is the speed a program operates, measures in hertz or gigahertz(one billion cycles per second), the faster the clock speed the faster instructions are fetched decoded and executed - typical speed for a PC is 2Ghtz and 4Ghtz

How does clock speed affect a CPU performance

Access speed of main memory

Reading from and writing to in main memory is slower than the speed at which the processor can work

Whats one factor that can slow down a computer

Access speed is faster from cache compared to RAM, the more cache a computer has, the more data and instructions can be held in cache and made available more quickly which improves the processor performance

How does cache size affects the performance of a CPU

A high number of cores means parallel processing can take place with more instructions being executed simultaneously

How does number of cores affect a CPU performance

Because the computer isn’t designed to have multiple cores

Explain a reason why a computer won’t work faster with multiple cores

small computers built into an equipment that performs a specific instruction

What are embedded systems

1. Reliable

2. Minimal resources

3. Simple user interface

4. Sensors that measures external stimuli and react accordingly

5. Limited operating systems so doesn’t have to be loaded when machine is switched on

6. Written in machine efficient language so it executes as fast as possible with minimal energy

7. Program which controls the equipment is held in ROM

Characteristics of embedded systems

1. Primary storage (RAM, ROM and virtual memory)

2. Secondary storage ( magnetic devices(HDD), SSD and optical devices

List and give examples on the types of storage

They are storage devices stored away from the computer

What are off line storage devices

It’s the main memory where data or programs that is currently being executed by the processor are stored temporarily

What is RAM

when a program is being executed, it has to be loaded from the hard disk into the main memory so the processor can access its instructions

Need for primary storage

Reading from or writing to hard disk is slower compared to the speed of the processor are

Why doesn’t the processor get instructions straight from hard disk

They temporarily hold data currently being run from the RAM when the RAM has not enough main memory and the data will be swapped between the virtual memory and main memory to be executed because the virtual memory has a slower access speed; although the time used in swapping might be more than the time used in executing

What are virtual memory and uses

• RAM volatile while ROM is non volatile

• RAM , memory can read or written to while ROM, memory can only be read from

• RAM stored data or operating system which is currently in use while ROM stores BIOS/bootstrap loader that loads the operating system or required to start up the computer

Difference between RAM and ROM

Capacity

Durability

Cost

Speed

Portability

Reliability

Factors to consider in a device

That have moving parts so they are susceptible to damage, and vulnerable to magnetic fields, less portable so required for desktop purposes and slow to read from or write to . Alothiugb they can be internal or portable (portable are offline storage devices)

Explain magnetic devices

1. Has no moving part so less susceptible to damage , not vulnerable to magnetic properties

2. Quieter

3. Has no moving part so thin

4. Lower power consumption

5. Faster access times

6. Lighter

7. Run cooler

benefits of SSD compared to HDD

Magnetic sticks( pen drive)

Magnetic cards(XD AND SD in cameras)

Portable devices

USB

SSD

Examples of solid state

Lasers write data to the disc and read data from it, CDs(CD-RW rewrite able, CD-R recordable, CD- ROM read only), DVDs and blue ray

Has moving part so slower to read from and write to, slower access speed and data transfer speed

Explain optical devices

Expensive

Thinner forms so they can break easily

Disadvantages of SSD

Adv: cheaper and higher capacity

Examples: hard disks and magnetic tape

advantages of magnetic devices and examples

Cheaper and longer life

Advantages of optical devices

• moving parts so slower access speed or data transfer speed

• Can degrade or become scratched overtime

Disadvantages of optical devices

They send signals to coordinate the fetch execute cycles, decoding instructions and running the fetch execute cycle

What’s the control Unit