central processing unit architecture Flashcards
AS-level
purpose and roles of the control unit
–directs and co-ordinates other parts of computer system
–controls operations of computer system
–fetches computer instructions
–decodes each instructions
–executes these instruction.
purpose and roles arithmetic logic unit
– a unit which performs arithmetic operations
–and bit shifting operations
– logic operation(AND,OR,XOR)
–designed to perform integer calculation
define operand
part of the computer instruction which specifies what data is to be processed
define opcode
is the instruction that is executed by the cpu
purpose and role of registers
–small piece of memory
–part of the processor
–temporary storage of data which is about to or had been processed
difference between general purpose and special purpose registers
general purpose registers holds the temporary data while performing difference operations.
special purpose registers holds the status of a program
define program counter
stores the address of next instruction to be fetched
define MAR
stores memory address where data is to be read from
define MDR
stores data that has just been read from memory
define CIR
stores the instruction that is currently being executed
define IX
index register used for indirect addressing .
define ACC
(accumulator) is the register where the data is worked on (general purpose register).
define status register
is interpreted as independent flags each flag is set depending on an event .
purpose and role of a system clock
–every computer contains an internal clock that regulates the rate at which the instruction are executed
–CPU requires a fixed number of clocks cycles that executes each instructions
– used to synchronize all the operation.
state the various components of the computer system that transfers data
–data bus
–address bus
–control bus
define data bus
–carries data between processor and memory
–bi-directional bus
– used to exchange data
define address bus
–uni- directional
–that carries signal related to memory address
– between processor and memory
define control bus
–transmits signals between control unit and other components
–bi-directional
what are the factors affecting the computer performance
–data bus width
–clock speed
–cache memory
–number of cores
define how the data bus width affects performance
– the width of a bus determines the number of bits that can be simultaneously transferred
–increasing the width of a data bus increases the number of bits that can be transferred
– hence improve processing speed as fewer transfers are needed
define how the clock speed affects performance
–one F-E cycle is run on each clock pulse
–so the clock speed dictates the number of instructions that can be run per second
–the faster the clock speed the more instructions can be run per second
define how the cache memory affects performance
can also improve processor performance , it is similar to RAM, cache uses SRAM so they have faster access time as there is no need to keep refreshing. cache memory stores frequently used instructions and data that needs to be accessed faster , this improves processor performance
define how the number of cores affects performance
–each core processes one instruction per clock pulse
–more cores mean that sequence of instructions can be split between them and so more than one instruction is executes per clock pulse
–more cores decreases the time taken to complete task
define a port
acts as an interference between computers and other peripheral devices. female part of connection
benefits of connecting peripheral devices using a USB port
– fast data transfer
useful when transferring large files such as video files
–automatic connection/plug and play
so usually there is no need to install separate drivers
–USB is now an industrial standard
all new computers will be equipped by USB port
–device may be powered or changed through USB
external devices could be charged while working at the computer
use of HDMI cables
– helps to connect more monitors
– hdmi ports allow to output both audio and visual
–they support high definition signals
–faster data transfer
–hdmi increases the bandwidth making it possible to supply the necessary data for high quality sound and visual effects
advantages of HDMI
– current standard for modern televisions and monitors.
–allows for a very fast data transfer rate
–improved security, helps prevent privacy by the help of HDCP
–supports modern digital system
disadvantages of HDMI
–not a very robust connection(easy to break connection when simply moving devices)
–limited cable length
advantages of VGA
–simpler technology
–only one standard available
–easy to split the signals and connect a number of devices from one source
–the connection is very secure
–VGA supports a higher refresh rate
disadvantages of VGA
– it does not support audio
–outdated as modern laptops and computers rarely have a VGA port
–easy to bend the pins when making connections
describe the process fetch-execute cycle
– pc holds the address of the next instruction to be fetched
– the address in program counter is copied to MAR
–program counter is incremented
–the instruction is copied from address stored in MAR to MDR.
–then instruction from the MDR is copied to CIR
instructions of the F-E cycle
MAR<=[PC]
PC<=[PC]+1
MDR<=[[MAR]]
CIR<=[MDR]
state the purpose of double brackets
the contents of MAR is an address , it is the contents of that address which is transferred to MDR
what is meant by interrupt
a signal from source/device
telling the processor that its attention is needed
example of hardware interrupt
printer out of paper
example of software interrupt
run-time error
a running program needs input
