OCR Computer Science GCSE //CPU EXAM WITH ANSWERS [100% PASS]

OCR Computer Science GCSE //CPU EXAM WITH ANSWERS [100% PASS] CPU - Central Processing Unit executes instructions, processes data, fetches data and stores data into main memory once executed (performs the fetch decode execute cycle). It make a computer system function MAR - Memory Adress Register holds the address of the current instruction that is to be fetched from memory MDR - Memory Data Register holds the contents found at the address held in the MAR Main Memory/Primary Storage the component of the computer that holds data, programs and instructions that are currently in use Address Bus carries memory addresses for locations to be read from or written to Data Bus carries data between the CPU and main memory Control Bus carries control signals around the CPU and memory ACC - Accumulator holds the data being processed and the results of processing PC - Program Counter holds the memory address of the next instruction to be fetched from main memory ALU - Arithmetic Logic Unit performs arithmetic (add/subtract) and logical (AND, OR) operations CU - Control Unit Follows the fetch decode execute cycle and controls the flow of data within the CPU.. Cache a small amount of memory which temporarily holds instructions and data that the CPU is likely to reuse. It is very fast and sits between the CPU and main memory. It is faster to access than RAM. The bigger the cache, the less time a processor has to wait for instructions to be fetched. RAM - Random Access Memory is a short term data storage that holds data and instructions that are currently in use by the processor, is volatile (loses power when turned off) ROM - Read Only Memory permanent instructions that cannot be changed, non-volatile. It allows a computer to start up or regenerate each time it is turned on I/O Controllers used to allow an interface between a hardware device external to the motherboard (e.g. a keyboard) and the processor itself System Buses