Chapter 16: Machines & Computational Models Flashcards
Main features of Von Neumann Architecture
- Data & instruction both stored as binary digits together in the same RAM
- Instructions fetched from memory serially
- The processor decodes & executes an instruction before fetching the next instruction
- The cycle continues until no more instructions are available
PC
Holds the memory address of the next instruction to be fetched. Increments by 1 as the FDE cycle runs
MAR
Contains the memory address of either the next instruction to be fetched or the address of where the results of the current process are to be stored
MDR
Holds the contents found at the address held in the MAR, or data which is to be transferred to main memory
IX
Register used when performing operations involving index addressing
Multi-core processors
Can work together on the same program (parallel processing) or they can work together on multiple programs (multitasking)
Parallel processing
Multiple tasks are completed at the same time by different processors
Serial processing
One task at a time is completed by one processor
Multiple cores
Having multiple cores means that a computer can potentially accomplish more tasks in a given amount of time
Virtual memory
Area of the hard disc drive that is used as temporary RAM when the actual RAM is full. It is the use of secondary storage as additional primary memory
When is virtual memory used?
Used when the amount of RAM needed to hold all running programs & data is greater than the amount of RAM available to the computer
How virtual memory works
- OS uses part of secondary storage to act as part of main memory (1)
- OS moves programs that are not immediately needed out of main memory (1) & stores them in virtual memory (1) using paging (1)
- Active programs are swapped into main memory from virtual memory (1)
SRAM
Type of RAM that retains data bits in its memory as long as power is being supplied & doesn’t need to be constantly refreshed
SRAM features
- Cache uses SRAM
- Uses flips flops to hold each bit of memory
- Doesn’t need to be constantly refreshed
Algorithm
A precise method for solving a problem, consisting of a sequence of step- by- step instructions
Input
The process of entering data into a computer/ The information entered into a computer system
Output
The process of displaying data that has been processed or stored/ The information that a device displays
Process
Performing a series of actions on the inputs according to a given set of rules
Computational models
Describe how algorithms are executed by a machine
Sequential
Following instructions in an algorithm step by step in a specific order, one after the other, from start to finish
Parallel
Processes are distributed between 2 or more processors. Each separate part of the algorithm that each processor processes can be combined together
Multi- Agent
Separate tasks/ algorithms are processed by different systems to perform a particular function. Each agent is autonomous & acts independently and under its own control
