1. Internal Components of a Computer Week 2 The Bus Main Memory Processor

2. The Bus: what is it? The Bus is made of a number of wires called tracks made up on a printed circuit board. Data is carried through an 8 bit or 16 bit or 32 bit bus. The example here is 8 bit. Each wire of the bus carries 1 of 2 signal levels: 1s and 0s. Different binary values are placed on the bus, and therefore, the patterns of 1s and 0s will change. Whatever value is placed on the bus: it is potentially available to everything connected to the bus. 01011001 10110011

3. Main Memory The memory consists of many storage locations which have addresses. These storage locations contain values: an instruction (computer program instruction), hexadecimal number, character, or yes or no. Imagine that these addresses use the decimal system starting at Zero and then the binary number 110010 lives at address number 5070. ? 5070 70 5072 ? 5074 50

4. Data program instructions are held in memory and represented as a number.Data program instructions are held in memory and represented as a number. Each location can hold one byte (8-bits) of data. However, if the memory location contains more than 8 bits (16, 24, 32, 64, 128 bits) it is known as a word.Each location can hold one byte (8-bits) of data. However, if the memory location contains more than 8 bits (16, 24, 32, 64, 128 bits) it is known as a word. Now look at the assembly language mnemonics: MOV Bx, [5070].Now look at the assembly language mnemonics: MOV Bx, [5070]. What does this line mean?What does this line mean? Click on slide for Answer.Click on slide for Answer. Main Memory: How do Memory Storage Locations Work? It is an instruction telling the processor to take the number in location 5070.

5. How do the instructions reach the processor? The memory and the processor are connected to the system bus.The memory and the processor are connected to the system bus. MemoryProcessor DATA BUS ADDRESS BUS CONTROL BUS

6. The Process The Processor picks the address for the first instruction and tells the Memory which address is to be used. The Address Bus is only one way because the Processor only needs to instruct the Memory as to which address needs to be used. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

7. The Process The Processor picks the address for the first instruction and tells the Memory which address is to be used. The Address Bus is only one way because the Processor only needs to instruct the Memory as to which address needs to be used. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

8. The Process The Processor picks the address for the first instruction and tells the Memory which address is to be used. The Address Bus is only one way because the Processor only needs to instruct the Memory as to which address needs to be used. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

9. The Process The instruction is put on the Data Bus by the Memory. The processor takes the instruction, interprets the meaning, then asks for the value of the memory storage location 5070, which is 50, to be put on the Data bus. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

10. The Process The instruction is put on the Data Bus by the Memory. The processor takes the instruction, interprets the meaning, then asks for the value of the memory storage location 5070, which is 50, to be put on the Data bus. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

11. The processor requests the next instruction to go on the bus. This is interpreted by the processor, which requests the value in the memory storage location 5072: this is 70. The Process Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

12. The next instruction is loaded onto the Data Bus by the Memory to go to the processor. The processor interprets this... … to add the numbers together. The Process Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

13. The Process The processor asks for the next instruction to be loaded onto the bus. It writes the address where the results will be stored. This is loaded onto the bus, followed by the result which will be stored in 5074. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

14. The Process The Control Bus carries a signal to tell the memory whether a read or write operation is taking place. 1 means read 0 means write. Main Memory or Intermediate Access Store Processor Control Bus Data Bus Address Bus

15. Conclusion The memory consists of storage locations which have addresses.The memory consists of storage locations which have addresses. The processor knows the address where the instructions are held in memory.The processor knows the address where the instructions are held in memory. The processor and the memory are connected to the system bus: the data bus, the address bus and the control bus.The processor and the memory are connected to the system bus: the data bus, the address bus and the control bus.