1. Computer Organization - 1

2. INPUT PROCESS OUTPUT List different input devices Compare the use of voice recognition as opposed to the entry of data via the keyboard Components of a system

4. CPU or The Processor Carries out instructions and tells the computer what to do [CU] Performs arithmetic calculations and data manipulation [ALU] Holds data and instructions which are in current use. [Memory registers]

5. Control Unit (CU) That part of the computer which accesses instructions in sequence, interprets them and then directs their Implementation – literally in control. What it does: 1.Directs the entire computer system to carry out stored program instructions 2.Communicates with both the arithmetic logic unit and main memory 3.Uses the instruction contained in the Instruction Register to decide which circuits need to be activated 4.Co-ordinates the activities of all peripheral and auxiliary storage devices linked to the computer.

6. Arithmetic Logic Unit (ALU) The part of the CPU where arithmetic and logic operations are performed. What it does: 1.Executes arithmetic operations like addition, subtraction, multiplication and division 2.Executes logical operations which compare numbers, letters and special characters (=, ) 3.Performs logic functions such as AND, OR and NOT Registers: 1.Accumulator is used to accumulate results. It is the place where the answers from many operations are stored temporarily before being put out to the computer's memory 2.General-purpose registers hold data on which operations are to be performed by the arithmetic logic unit.

7. Primary Memory part of the computer that holds data and instructions for processing When we load software from any external storage, it is stored in the Primary Memory There are two types of computer memory: RAM and ROM

8. RAM / ROM Random Access Memory (RAM) Where the programs get stored CPU fetches program instructions from the RAM CPU stores calculation results here Can read or write to it When computer is switched off RAM is lost Read Only Memory (ROM) Only read this memory used for storing special sets of boot up instructions. When computer is turned off ROM is kept alive.

9. Cache Memory High speed Located in CPU itself Stores current data

10. Memory Access-Address Bus Series of wires connecting CPU and memory unit and is used to identify locations (addresses) within memory The width of the address bus (that is, the number of wires) determines how many unique memory locations can be addressed. Modern computers have as many as 36 address lines, which enables them theoretically to access 64 GB (gigabytes) of main memory

11. Microprocessors Devices similar to CPU with a single program stored in non-volatile memory Used to control various devices – Control fuel injection system s in cars – Washing machine controls – Photocopier controls – Security systems – Automatic cameras (exposure, image conversion)

12. 12 Microprocessor Architecture The microprocessor can be programmed to perform functions on given data by writing specific instructions into its memory. – The microprocessor reads one instruction at a time, matches it with its instruction set, and performs the data manipulation specified. – The result is either stored back into memory or displayed on an output device. Single instruction fetch – decode – execute was Von Neumann design. At present we use multiple pipeline architecture

13. 13 The Address Bus – 16 bits wide (A 0 A 1 …A 15 ) can access locations with numbers from 0 to 65,536. Or, can access a total of 64K addresses. – “Unidirectional”. Information flows out of the microprocessor and into the memory or peripherals.

14. 14 The Data Bus – 8 bits wide (D 0 D 1 …D 7 ) – “Bi-directional”. Information flows both ways between the microprocessor and memory or I/O.

15. 15 The Control Bus – There is no real control bus. Instead, the control bus is made up of a number of single bit control signals.

16. 16 Microprocessor Initiated Operations These are operations that the microprocessor itself starts. These are usually one of 4 operations: – Memory Read – Memory Write – I/O Read (Get data from an input device) – I/O write (Send data to an output device)

17. 17 The Read Operation – To read the contents of a memory location, the following steps take place: The microprocessor places the 16-bit address of the memory location on the address bus. The microprocessor activates a control signal called “memory read” which enables the memory chip. The memory decodes the address and identifies the right location. The memory places the contents on the data bus. The microprocessor reads the value of the data bus after a certain amount of time.

18. 18 Dimensions of Memory Memory is usually measured by two numbers: its length and its width (Length X Width). The length is the total number of locations. The width is the number of bits in each location. – The length (total number of locations) is a function of the number of address lines. # of memory locations = 2 ( # of address lines) So, a memory chip with 10 address lines would have 2 10 = 1024 locations (1K) Looking at it from the other side, a memory chip with 4K locations would need Log 2 4096=12 address lines

19. 19 Chip Select Usually, each memory chip has a CS (Chip Select) input. The chip will only work if an active signal is applied on that input. To allow the use of multiple chips in the make up of memory, we need to use a number of the address lines for the purpose of “chip selection”. – These address lines are decoded to generate the 2 n necessary CS inputs for the memory chips to be used.