CPU

CPU

1. Central Processing Unit

2. The brain

3. Processes all the data and instructions that make the systems work

4. Processing power of a CPU depends on different things like clock speed, number of cores and cache sizes

5. The Control Unit

   • In overall control of the CPU
   • Controls the flow of data

6. The Arithmetic Logic Unit

   • Does all the calculations
   • Performs logic operations such as AND, OR and NOT and binary shifts
   • It contains the accumulator register

7. The Cache

   • Very fast memory in the CPU
   • Slower than the registers but faster than RAM
   • Have very low capacity and are expensive compared to RAM and secondary storage

8. Fetch-Decode-Execute Cycle

   • Fetch
     • 1) Copy memory address for the program counter to the MAR 2) Copy the instruction stored in the MAR address to the MDR 3) Increase the program counter to point to the address of the next instruction, ready for the next cycle
   • Execute
     • The instruction is performed. This could be load data from memory, write data to memory, do a calculation or logic
   • Decode
     • The instruction in the MDR is decoded by the CU. The CU may then prepare for the next step.