systems architecture

• Fetch-execute Cycle

  Instructions are fetched one by one from main memory, decoded, and then executed by the processor. This cycle repeats until the program is

  complete.
• CPU (Central Processing Unit)

  A chip within the computer which controls the operation of all parts of the computer and decodes then executes program instructions.
• ALU (Arithmetic Logic Unit)

   The part of the CPU responsible for arithmetic and logical operations.
• Processor Cache

  High speed memory built into the CPU. Instructions are copied to cache memory allowing them to be accessed more quickly and therefore

  increasing the speed of the CPU.
• Register

  A small area of memory within the CPU where data is stored temporarily to avoid the delay in copying to and from main memory,
• Von Neumann Architecture

  The design on which most computers are based. It defines several

  registers along with the fetch-execute cycle and how the CPU interacts with main memory.
• MAR (Memory Address Register)

  A register. It contains the address of the instruction currently being read from or written to main memory.
• MDR (Memory Data Register)

  A register. It contains the instruction which has just been copied from main memory.
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  Program Counter

  A register. It contains the address of the next instruction to be fetched from memory. It is updated each time a new instruction is fetched to contain the address of the next needed instruction.
• Accumulator

  A register. Stores the result of the last operation.
• Clock Speed

  How many instruction cycles the CPU can deal with in a second. Measured in MHz or GHz. Faster is better.
• Cache Size

  The larger the amount of cache the CPU has the more instructions it can store without having to transfer to main memory and therefore the faster it will perform.
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  Cores

  Some CPUs have more than one core, each containing its own ALU and registers and therefore capable of carrying out instructions independently. The more cores, the more instructions the CPU can process at once and therefore the faster it performs.
• Embedded System

  Specialist hardware and software build into a device with a single specific

  purpose. They are usually found within appliances such as washing machines.