computer organisation and architecture Flashcards
internal components of a computer
processor
main memory
address bus
data bus
control bus
I/O controllers
role of processor
executes machine instructions that are fetched from main memory locations.
processor selects a memory location by placing the address of the location on the address bus.
data processed by machine instructions is fetched along the data bus from main memory and the results of processing are returned in the same way
control bus is used by the processor to assert actions and to allow devices to grab the attention of the processor via the interrupt mechanism when a key is pressed
role of main memory
memory that can be accessed directly by the processor
main memory consists of a contiguous block of read/write, randomly accessible storage locations where instructions or data are stored as binary sequences
role of address bus
underictional and used to select a specific memory location containing a word of data or an instruction.
it carrys the address of the desired location on its bus. the address bus is also used to address I/O ports during input/output operations
role of data bus
provides a bidirectional path for moving data and instructions between system components
role of control bus
bidirectional bus which is used to transport control signals that manage and orchestrate the operations that take place in a computer system between components.
(includes exchanging status signals between the components and transmitting clock signals required for the coordination of instructions).
role of I/O controllers.
used to buffer data being sent between the processor and the device, so the processor does not have to wait for the individual device to repond
concept of bus
transfer data between components
address bus
used to specify the address of a memory location to either read data from or write data to that memory location
control bus
used to send control signals that manage and orchestrate the operations that take place inside a computer system
data bus
used to transfer data and instructions
bidirectional
difference between von neuman and harvad
Harvard - execution of instructions are faster as fetching of code and data are simultaneous
Von Neumann - instructions and data have combined memory spaces (used extensively in general purpose computing systems)
where are harvad architecture used
embedded systems such DSP systems
where are von neuman used in
general purpose computing systems
concept of addressable memory.
memory in a computer that can be accessed by the computer’s processes and is assigned to a particular place in that computer’s processor.
stored program concept
Instructions are stored in the main memory. Instructions are then fetched decoded and executed by the processor which allows the program to be moved in and out of the main memory
role of arithmetic logic unit
part of the processor that processes and manipulates data.
role of control unit
controls the fetch decode execute cycle and sends signals to other components of the cycle
role of clock
To control the speed at which instructions are retrieved and processed in the CPU
role of generous purpose systems
designed to perform many tasks (tablets, PC)
role of program counter
stores memory address of the next instruction to be fetched and executed
role of current instruction register
stores the instructions that is currently being executed by the processor
role of memory address register
stores the memory location where data in the MBR is about to be written to or read from.
role of memory buffer register
holds the data that has just been read from or is about to be written to main memory.
role of status register
to store information about instructions received from machines
fetch stage of fetch decode execute cycle
- Contents of Program Counter transferred to Memory Address Register
- Address bus used to transfer this address to main memory
- instruction transferred using the data bus
- Contents of addressed memory location loaded into the Memory Buffer
Register - Transfer content of Memory Buffer Register to the Current Instruction
Register
decode stage in fetch decode execute cycle
- instructions held in the CIR is decoded by the CU (where the instruction is split – - into opcode and operand)
During the decode and execute stages of the fetch-execute cycle the instruction
that is being processed is stored in the CIR. Explain why the instruction could
not be processed directly from the MBR.
- To carry out the instruction other data may need to be fetched
- Further memory fetches would overwrite the contents of the MBR
execute stage in fetch decode execute cycle
- Any data required by the instruction that isn’t present in registers is fetched
- The instruction is carried out
- Results of any calculations are stored in general purpose registers or main memory
processor instruction set
group of instructions that it can carry out
what does instructions consist of
an opcode and one or more operands (value, memory address or register).
immediate addressing
Immediate addressing: the operand is the datum.
direct addressing
the operand is the address of the datum.
interupt
Allows the currently executing process to be suspended
So that a device that needs the attention of the processor can be dealt with
why is it important to save the volatile environment while the interrupt is being serviced
So that the currently running process can be returned to
As the interrupt will change register values
6 factors that affect processor performance
multiple cores
cache memory
clock speed
word length
address bus width
data bus width.
effect on processor performance of multiple cores
parallel processing can take place, therefore the speed of execution is increased
effect on processor performance of cache memory
increasing size of cache, more data and instructions can be stored there, resulting in programs running faster
effects on processor performance of clock speed
increasing clock speed causes instructions to executed at a faster rate.
effects on processor performance of word length
increasing word length means the processor can access a larger amount of memory through direct accessing and could also allow the processor to have a larger instruction set
effects on processor performance of address bus width
increasing width increases number of addressable locations and allows more memory to be installed on the computer
effects on processor performance of data bus width
increasing width increases rate of data transfer
laser printer
bitmap of image built in memory from page description
charge applied to drum
laser beam directed at drum
mirror is used to direct laser beams
where laser strikes drum charge is discharged
charge applied to toner
toner sticks onto where the laser struck
paper passed over drum and toner transfers to it
positively charged transfer roller assists transfer of toner to paper
heat fuses onto paper
four drums are are required for colour printing
RFID scanners
RFID scanner sends signal;
Signal induces current in RFID transponder
RFID transponder sends data by radio
RFID signals processed into a format suitable for querying the database
query used to check if there is already a record for the product in the database
Explain why the product manufacturers or supermarket owners might prefer the individual products to be identified using barcode labels
Barcodes are cheaper than RFID tags
Higher cost of RFID tags would be added on to prices
Explain why the warehouse owners might prefer the individual products to be identified using RFID tags
the RFID tags could be read without removing products from their pallet;
RFID tags can be read from a distance (than barcodes)
Describe the principles of operation of an optical disk drive that is used to read data
from an optical disk such as a CD-ROM or DVD-ROM
light is shone at disk
light is reflected back from disk which is measured
Disc spins at constant linear velocity
Data is stored on one/spiral track
Continuation of land reflects light whereas transition between land and pit scatters light
Transition between land and pit indicates a 1 and continuation of land represents 0
