1.1 System Architechture

1.1 System Architechture

1. System Buses

   • Used to reduce the amount of data collisions. A hue is a set of parallel wires connecting two or more independent components in a computer system
   • Data Bus - Carries instructions from the main memory to the processor
   • Address Bus - Carries addresses from processor to main memory, it is unidirectional
   • Control Bus - Instructs which data will be travelling to and from memory

2. Internal Components - The Processor, Main Memory (RAM, ROM, EEPROM), I/O Controllers, Buses

3. External Components - Keyboard, mouse, printer, disk drives, I/O Devices/ I/O Ports, Secondary Storage (External Hard drive)

4. ROM - Read Only Memory - Bootstrap ladder is held in ROM, gives the instruction to start up the Operating System

5. EEPROM - Electronically Erasable Programmable Read Only Memory, e.g sim cards/flash memory. Instructions can be erased electronically

6. I/O Controllers - These are used to allow an interface between a hardware device external to the motherboard and the processor. I/O Controllers are used for: Keyboard, Mouse, Disk Drive

   • Control Unit - Low of data within the CPU

7. Embedded Systems - A computer system within another device e.g. central heating system, dishwashers, fridges, washing machines

   • Hertz - Number Of Cycles Per Second
     • Processor Speed - Measured In Hertz
     • Typical speeds have spanned across MHz and GHz

8. The purpose of the CPU is to carry out program instructions. Each CPU is designed to execute a specific group of instructions. The CPU carries out a series of functions in a continuous cycle

9. The CPU control unit automatically checks cache for instructions before requesting data from RAM. This saves fetching the instructions and data repeatedly from RAM – a relatively slow process which might otherwise keep the CPU waiting. Transfers to and from cache take less time than transfers to and from RAM

10. The motherboard is a circuit board that connects the CPU to the memory and all the other hardware. The CPU sits on the motherboard (also called the logic board).

11. Buses are circuits on the motherboard that connect the CPU to other components. There are many buses on the motherboard. A bus moves instructions and data around the system. The speed of a bus is measured in megahertz (MHz). The faster the bus, the faster data is communicated. The speed of the motherboard is defined by the bus speed.

12. Bridges manage how data and instructions are transferred between the CPU, memory and other devices. Many PC motherboards use a northbridge and a southbridge to connect devices: The northbridge connects the CPU, RAM and GPU through the FSB. The southbridge connects to the northbridge. All other hardware, such as the hard drive, connects to the CPU through the southbridge.

13. ROM (read only memory) is a flash memory chip that contains a small amount of non-volatile memory. Non-volatile means that its contents cannot be changed and it retains its memory after the computer is turned off.

14. PROM (programmable read-only memory) - manufactured as blank ROM. PROM chips can be bought cheaply and programmed directly by a programmer. They are not rewritable so they can only be programmed once.

15. EEPROM (electrically erasable programmable read-only memory) - popular in PCs and smartphones as the firmware can be easily updated by the manufacturer. This is similar to a rewritable CD in that the chip can be reprogrammed.

16. Memory Data Register - Backs Up Memory

17. More instructions can be carried out per second if there is a faster clock speed

18. A processor with more cores allows more instructions to be carried out simultaneously

19. Bigger caches allow space for frequently used instructions and data

20. Embedded Systems provide specific, pre-defined actions

21. ALU - Arithmetic Logic Unit, performs arithmetic calculations

22. Cache - Frequently used instructions and data is held there