Systems architecture (1.1) GapFill

In a computer system, components are arranged so that the CPU is connected to input and output devices as well as to  an external clockan embedded systemdata storagea program counter. The CPU is responsible for processing all of the operations that need to be carried out by the computer and is composed of the  ALU (Arithmetic Logic Unit)data busRAMcontrol bus, the CU (Control Unit), registers and  cachesecondaryvirtualread-only memory.

The CPU runs in a fetch-execute cycle to retrieve one instruction, carry out that instruction, retrieve the next instruction and so on. The CPU uses  heatsinksclocksALUregisters to store the data that is used in this process. The fetch-execute cycle is carried out as follows:

• The memory address of the next instruction to be executed is copied from the  PCALUCUMDR to the MAR
• This value is  doubledcopied to the MDRincreased by 1copied to the MAR while the data stored in the memory location pointed to by the MAR is copied into the MDR
• The instruction is copied from the  PCCUALUMDR to the CIR
• The instruction is then decoded by the  CUaccumulatorALUcache memory
• The instruction is executed

Factors which affect the performance of the CPU include the number of  busesinput/output devicesuserscores, the CPU's  memorycacheclockaccumulator speed and the amount of available  secondary storageRAMROMcache memory.

Sometimes a computer may not act as a standalone device, but instead be built into a larger device to perform some specific task. This sort of computer is known as  an embedded systema nested systeman iterative systeman open-source system.