System Architechture, Memory And Storage Flashcards
(21 cards)
What are the 3 basic elements of computer systems
Input
Process
Output
The element of input in a computer system
Data feeds into the system from input devices
The element of process in a computer system
The data collected needs to be processed and actions need to be carried out. This means carrying out calculations, sending instructions to other devices or transferring data from different areas of memory.
The element of output in a computer system
Once processed or acted on, the result is presented via an output device
Common central processing unit components
ALU (arithmetic logic unit)
CU (control unit)
Cache
What does the ALU do
Where calculations are carried out. These include mathematical tasks, logic tests and data comparisons
What does the cache do
A cache is a small memory of very fast memory within the CPU used to store frequently used data and instructions when RAM is full as it is easy to access with it being close to the CPU
What does the MAR do
This is the location address in memory of the next piece of data or instruction that the CPU needs to be fetched or stored
What does the MDR do
An instruction or piece of data fetched from memory is stored here temporarily until its used
What does the program counter do
This continuously provides the CPU with the memory address of the next instruction in the cycle to be fetched
What does the accumulator do
This is where the results of calculations carried out by the ALU are temporarily stored until they are needed
What does the bus do
The bus is a physical pathway shared by signals to and from components of a computer system such as input and output devices; the arrows in the diagram represent wires and circuit boards
The FDE cycle describes how the CPU…
Fetches instructions
Decodes them
Carries out (or executes) the instructions
What happens at the fetch stage of the FDE cycle
The processor fetches the instructions from memory and uses the program counter to keep track of where it is
What does the CPU contain
Memory
Input/output devices
Control unit
ALU
Registers
What does the control unit do
Sends signals to control the flow of data around the CPU
What are registers
Small and very fast memory with a specific purpose
What happens at the fetch stage of the FDE cycle
Data is fetched from memory, the address of the next instruction to be executed is copied from the PC to the MAR.
The actual data/instruction stored in the MAR is copied to the MDR
The pc is incremented to be executed
What happens at the decode stage of the FDE cycle
The control unit looks at the instruction and works out what’s needs doing
What happens at the execute stage of the FDE cycle
This depends on the instruction, it can be:
Write data/instructions to the memory
Repeat this cycle to fetch additional data/instructions from the memory
Carry out a calculation using the ALU
