Systems Architecture

Systems Architecture

1. Fetch, decode and execute cycle

   • Fetch - copy the memory address from the program counter(PC) to the memory address register(MAR), then copy those instructions into the memory data register(MDR). Finally increase the program counter to the address of the next instruction for the next cycle.
   • execute - the instruction is then performed which may be loading data from memory
   • Decode - the instruction in the MDR is decoded by the control unit(CU), which may prepare for the next step by loading values into the MAR or MDR

2. CPU

   • central processing unit
     • It is the brain of the computer and processes all the data and intructions that make the system work
   • ALU - Carries out arithmetic and logic operations AND OR NOT
   • CU - It controls the flow of data, and decodes instructions in the MDR
   • cache - Quick access memory inside the CPU , it stores regularly used data so that the CPU can access it quickly when needed.

3. Von Neumann archit; A system where the cpu runs programs that are stored in memory. The programs consist of data and instructions that are stored in the memory address

   • MAR - a CPU register that holds memory addresses (locations) for data and instructions that the CPU needs
   • MDR - a CPU register that holds data and instructions from RAM
   • PC - holds the memory address of the next CPU intruction
   • Accumulator - the part of the ALU that stores the immediate results when doing a calculation
   • registers
     • Temporary data stored within the CPU, small amount of memory, faster access

4. stored program concept

   • A program that can be stored electronically in binary-number format in the memory device so the instructions can be modified by the computer
   • fixed program
     • A special purpose computer which has a program permanently wired in it

5. embedded systems

   • A system within a system, a computer built onto another device and is used to perform a specific task
   • Microwave, Dishwasher, Washing machine

6. chatacteristics

   • Clock speed - Number of instructions a single processor core can carry out per second (Hz). The bigger the clock speed the bigger the number of instructions carried out per second
   • Cache - The cache is data storage inside the CPU and is faster than RAM. The bigger the cache the quicker the access is to more data it needs to process. it is stored regularly.. you cannot upgrade the cache add to or change RAM
   • Cores - A processing unit found within the CPU, each core processes data independently of the rest. The more cores there is the more instructions it can carry out at once so the faster it can process a batch of data