ch4 Flashcards
features of the Von Neumann
architecture
1- has a central processing unit (CPU or processor)
2- a processor that can access data directly
3- computer memories that could store programs as well as data
4- stored programs made up of instructions that could be executed in sequential order
main components of the processor
1- arithmetic logic unit
2- control unit
3- system clock
4- immediate access store
Arithmetic logic unit (ALU)
component of a processor that carries out all arithmetic and logical operations
accumulator
temporary general purpose register which stores numerical values at any part of a given operation
job of control unit
Ensures the execution of instructions in the correct sequence. The CU ensures synchronisation of data flow and program instructions throughout the computer.
job of system clock
A system clock is used to produce timing signals on the control bus to ensure this vital synchronisation takes place
immediate access store
hold data temporirly that the cpu needs to access
register
temporary component in the processor that can be general or specific in its use that holds data and instructions as part of the fetch and execute cycle
job of general purpose register
holds data that needs to be frequently accessed by the cpu or by the programmer when accessing the cpu directly
job of specific purpose register
has a specific function within the cpu and holds the program state
index register
used when carrying out index addressing operations
status register
used when an instruction needs some sort of arithmetic or logical processing
address bus
carries the addresses throughout the computer (unidirectional bus)
data bus
carries data from from processor to memory (vise versa) and input/output devices
(bidirectional)
control bus
carries signals from control unit to other components of the computer (bidirectional)
four factors that effect the computers overall performance
1- width of the bus: the wider the bus the more bits can be transferred each time
2- clock speed: the higher the speed more number of FE cycles is done per second
3- cache memory: the higher the capacity the more instructions can be stored to be accessed b the cpu
4- number of cores: the higher the number the more instructions can be carried out simultaneously
fetch and execute cycle
the address in the pc is incremented by one and that address is then stored in the mar. mar holds the address of memory location that needs to be fetched. the mdr holds data that is read from or currently written to, the instructions in the mdr are then transferred to the cir to be decoded, the decoded instructions are then executed by the processor
what is an interrupt
a signal sent from the software or a device to the processor which will temporarily cause it to stop until error is fixed
handling interrupt signals
interrupt signals are checked at the end or beginning of each
FE cycle, and priority is checked; if priority is higher than current process, the current registers are stored on stack. the location of the interrupt is found. an isr is then used to handle the interrupt signals and when done the cpu is checked once again for interrupt signals until none is found
stored program concept
data that is stored in the same memory space
index register p1
stores a value that is added to the index to give a new address
status register p1
stores flags from the result of arithmetic or logical operation and interrupt flags
purpose of cu p1
-produces signals to ensure synchronization of data flow throughout the computer
-sends and receives control signals along the control bus
-manages the execution of instruction
purpose of interrupt p1
sends a signal to get the attention of the processor to fix an error
