sys architecture 1.1

sys architecture 1.1

1. FDE Cycle

   • 1.The memory address from the Program Counter is copied to the MAR
   • 2.An instruction is fetched from the address stored in the MAR
   • 3.The fetched instruction is stored in the MDR
   • 4.The value in the Program Counter is changed to point to the next instruction
   • 5.The fetched instruction is decoded by the control unit
   • 6.The decoded instruction is carried out (e.g. data is loaded to/from memory, calculated, program halted)
   • 7. cycle is repeated

2. Special purpose CPU registers Fast memory that store tiny amounts of data or instructions that the computer can access extremely quickly

   • Program Counter – Holds the memory address of the instruction for each cycle
   • MAR – Memory Address Register - Holds memory address about to be used by the CPU
   • Accumulator – Stores the results of the calculations done by the ALU
   • MDR – Memory Data Register - Holds data or instructions that have been fetched from memory

3. Factors that affect speed

   • Clock speed – Number of instructions that can be carried out in a second (Hz) – These days in Ghz (Billion)
     • Number of processor cores – Each core processes data independently of the rest. The more cores, the faster it can process. These days we have dual or quad cores but can have up to 6 or 8.
       • Cache size – A larger cache gives the CPU faster access to commonly used data. It is faster than RAM.

4. von neumann arch

   • Von Neumann Architecture Traditional computer architecture that forms the basis of most digital computer systems Neumann came up with the idea that programs and data could be stored in the same memory unit. In early computers (Harvard architecture) these were stored in separate memory units and entering or altering programs was harder.
     • Simple model of a computer system
       • input
         • process
           • memory ? storege
           • output

5. computer parts

   • cpu
     • CPU – Central processing Unit – This processes all of the data and instructions that make a computer system work
     • CU – Control Unit
       • Controls activities in the CPU (Such as flow of data between CPU and other parts) • Makes FDE cycle happens in order • Decodes instructions • Executes instructions
         • Makes FDE cycle happens in order
           • fetchs and exucutes
       • ALU – Arithmetic and Logic Unit
         • Performs logical operations (AND, OR, NOT)
           • Shift operations
             • Arithmetic operations (+,-, *, / )
         • cache
           • Sits between the CPU and RAM. Very fast. Holds frequently used data so that the processor doesn’t have to keep going back and forth to the RAM.

6. Embedded system

   • A computer system built into another device (usually designed for a specific purpose)
   • Devices that have embedded systems – Dishwasher, MP3 player, Washing machine, Microwave
     • Benefits of embedded system
       • Smaller than general purpose – Means microwaves/MP3 players can be more compact
         • Cheaper to produce than general purpose computers - Which can reduce costs
           • Tend to be more reliable than general use – Microwaves are less likely to break/malfunction