U4 Processor Fundamentals Flashcards
What is meant by the Von Neumann model?
- Uses a single processor
- Follows a linear sequence of fetch-decode-execute operations for the set of instructions; in order to do this, processor uses registers
What is the stored program concept?
Both instruction and data are stored in the computer memory itself
What are registers?
Smallest unit of storage of microprocessor; allows fast data transfer between other registers
What are General purpose registers?
Used to temporarily store data values which have been read from memory or some processed result
What are special purpose registers?
Only accessible by assembly language instructions and only holds either data or memory location(not both)
What does a Program Counter do?
Holds address of next instruction to be fetched
What does a Memory Data Register do?
Holds data value fetched from memory
What does a Memory Address Register do?
Holds address of location of program which is to be accessed
What does an Accumulator do?
Holds all values that are processed by arithmetic and logic operations
What does an Index Register do?
Stores a number used to change an address value
What does a Current Instruction Register do?
Once program instruction fetched, it is stored here and allows processor to decode and execute it
What does a status register do?
Dedicated registers containing information about the intermediate states or outcomes of various processes in the processor.
e.g. indicates if calculation has produced overflow error
What does the ALU do?
Processes instructions which require some form or arithmetic or logical operation
What does the CU do?
Fetches instructions from memory, decodes them and synchronises operations before sending to computer memory, ALU and input output devices to direct how to respond to instructions sent to processor
What does Immediate Store Access do?
Memory unit that can be directly accessed by a processor
What does a System Clock do?
Timing device connected to processor that is needed to synchronise all components
What are buses?
Set of parallel wires that allow carries data between components in a computer system
What is a data bus?
Bi-directional bus that carries data instructions between processor, memory and I/O devices
What is an address bus?
Unidirectional bus that carries address of main memory location or I/O device about to be used, from processor to MAR
What is a control bus?
Bi-directional bus that is used to transmit control signals from CU to ensure access or use of data and address buses by components of system. doesn’t lead to conflict
What is clock speed?
Number of pulses the clock sends out in a given time interval, which determines number of cycles CPU executes measured in Hz
What happens if clock speed increases?
More cycles per unit time, increasing performance
What is bus width?
Determines number or bits that can be simultaneously transferred
What happens if bus width increases?
Increases number of bits transferred per unit time, increasing processing speed and performance
What happens if cache memory is increased?
Cache memory stores commonly used instructions so more instructions can be stored and wait for CPU to wait for instructions to load decreases, so more cycles per unit time increasing performance
What happens when number of cores increases?
Each core simultaneously processes different instructions so the more cores, the faster processing time is, so performance is increased
What are ports?
Hardware which provides a physical interface between a device with CPU and a peripheral device - this is done because peripheral devices can’t directly connect to CPU
What is USB?
Universal Serial Bus can connect both input and output devices to processor through USB port
What is HDMI?
High definition multimedia interface can only connect output devices to processor through HDMI port
Transmits high bandwidth and high resolution video and audio streams
What is VGA?
Video Graphics Array can only connect output devices to processor through VGA port
What are the steps in the fetch-decode-execute cycle?
- PC holds next instruction to be executed
- Address in PC copied to MAR
- PC is incremented
- Instruction loaded to MDR from address held in MAR
- Instruction from MDR loaded to CIR
- Decode: Opcode and operand parts of instruction identified
- Execute: Instructions executed by CU sending control signals
What is an interrupt?
Signal from a program seeking CPU’s attention
What is the ISR and what does it do?
The interrupt service routine handles the interrupt by controlling the CPU
different ISRs used for different sources of interrupt
What is Assembly language?
Low-level programming language with instructions made up of an opcode and an operand
What is machine code?
Code written in binary that uses processor’s basic machine operations - every assembly language instruction translates into exactly one machine code instruction
What is symbolic addressing?
Symbols can be used to represent opcodes, labels can be used for addresses
What is absolute addressing?
Fixed address in memory
What is an assembler?
Software that changes assembly language into machine code for processor to understand
What happens on the first pass of a two-pass assembler?
Symbol table created to enter symbolic addresses and labels into specific addresses
Errors suppressed
What happens on the second pass of a two-pass assembler?
Jump instructions access memory addresses via table
Whole source code translates into machine code
