system architecture
Von Neumann architecture
the CPU
descries a computer architecture in which
the data and the program are both stored in the computers memory in the same place.
all instructions and data will be stored as binary digits in the same place
the central processing unit (CPU) carries out all the processing for the computer system by following the instructions given to it.
made form billions of transistors (electronic switches) that build the logic gates to presses the data and instructions
a clock chip is an electronic device that controls the timing of signals measured in GHz (Giga Hertz). it controls the speed in which a computer will process infomation
the Fech-Decode-execute cycle is the prosess of feching the instructuins from the memory, decoding them and then executing them. the CPU is constantly doing this
inside the processor
there are 2 vital component to the processor
the arithmetic and logic unit (ALU) caries out the calculations and logical decisions required by the program instruction
the control unit (CU) is responsible to decoding instructions and controls how data moves around parts of the CPU
to move information around the CPU there is are a number of busses. a bus is a communication channel which information can pass through
Data Bus carries data between the CPU and the memory
Control Bus carries control signals around the CPU and memory
Address Bus carries memory addresses for locations to be read from or written to
there are registers in the CPU which are memory locations within the CPU
Accumulator a register that stores the results of any calculations made by the ALU
memory address register (MAR) register that stores the location in memory to be used by the MDR that is where to locate data it needs to fetch or where to send it to where in needs to be stored
current instruction register (CIR) register that stores the most recently fetched instruction while it is being decoded or executed
Memory data register (MDR) register that is used to store any data fetched from memory or any data that is to be transferred to and stored in memory
program counter (PC) keeps track of the memory location for the next instruction
RAM and ROM
RAM (random access memory) is the main memory in which the computer stores the data, applications and operating systems while in use. RAM looses all of its data when the computer is turned off
ROM (read only memory) is the memory in which the start up file is stored and can only be read from ROM does not loose its data when the computer is turned off
cores
types of computer system
cache memory
cache memory is special high-speed memory used by a computer
it is located very close to the CPU for quick and easy access it also has dedicated connections for faster data transfer.
cache is very expensive memory compared to RAM
there is 3 levels of cache memory level 1 (L1) level 2 (L2) and level 3 (L3) the numbers show how far away form the CPU the cache memory is.
L1 cache is often located on the CPU module and runs at the same speed as the CPU
L2 cache is often part of the CPU itself and runs at the same speed as the CPU it is usually a bit bigger that level 1
L3 cache is further away from the CPU on the motherboard and is larger and slower than both L1 and L2 cache
you can get quad-core and dual-core processors quad- core can do 4 fetch-decode-execute cycles at the same time and dual-core and do 2 fetch-decode-execute cycles at the same time
dedicated system is a system that is designed to perform only one task
control system a system designed to control machinery
general purpose computer a system that can perform a wide range of tasks e.g. desktop system, laptop of tablet
embedded system a system within a product that controls the product e.g. fridge, microwave.