4 - processor fundamentals

Question 2

von neuman archirtecrue

Answer 2

• there is a processor - CPU
• processor has direct access to memory
• memory contains a stored program and data required by the program
• stored program consists of individual instructions
• the processor executes instructions sequentially

Question 3

components of the CPU

Answer 3

• CU
• registers
• ALU
• cache

Question 4

clock

Answer 4

used to synchronise processes
internal clock - controls cycles of activity within the processor
system clock - controls activities outside of the processor
- has a defined freq for its clock cycle (clock speed) - defines the minimum time separating successive activities

Question 5

registers

Answer 5

• close so quick access
• used for storage
• general purpose or specific (accumulator is the only general purpose)

Question 6

ALU

Answer 6

– carries out arithmetic and logical operations such as mathematical operations and comparisons or Boolean logic

Question 7

control unit

Answer 7

– coordinates the operations of a computer – communicates with components

Question 8

accumulator - ACC

Answer 8

a general purpose register that stores a value before/after execution of an instruction by the ALU

Question 9

CIR

Answer 9

stores the current instruction while it is being decoded and executed

Question 10

IX

Answer 10

stores a value - only used for index addressing

Question 11

MAR

Answer 11

stores address of a memory location or an I/O device

Question 12

MDR

Answer 12

stores data that has just been read from or is about to be written to memory

Question 13

PC

Answer 13

stores the adress of where the next instruction is to be read from

Question 14

SR

Answer 14

contains bits that are either set or cleared which can be referenced individually

Question 15

system bus

Answer 15

• buses transfer data between components
• each wire carries a single bit
• connects CPU to memory and I/O devices
• address, controll and data

Question 16

control bus

Answer 16

• transmits signal from CU to system components or from components to CU
• bi directional
• carries timing signals

Question 17

address bus

Answer 17

• carries an address
• adress is loaded from MAR and specifies a location in memory
• one directional - to a memory controller or I/O controlled not back to CPU

Question 18

data bus

Answer 18

• carries data
• from processor to memory or output device
• or from memory or input device to processor
• bi directional

Question 19

factors affecting performance

Answer 19

• processor type/ no. cores - multi core and parallel processing means multiple instructions can happen simultaneously
• bus width - ideally same as word length or half - larger bus width = more bits transferred at once
• clock speed - clock cycle defines shortest time an - - action can take
• cache - closer so faster to access

Question 20

word

Answer 20

a small number of bytes that can be handled as a unit by the comp system
- word length is defined by a comp eg 16b

Question 21

port

Answer 21

• provides a connection between 2 devices
• each I/O is connected on an interface called a port
• each port is connected to the I/O device controller which handles interaction between CPU and I/O device
• Internal if I/O device is an integral part of the computer system
• External allows connection to peripheral I/O device

Question 22

USB port

Answer 22

• Peripherals can connect using a USB port
• allows plug-and-play - don’t need a technician to connect devices - no skill required
• A device can be connected while the computer is switched on and automatically configured for use
• hierarchy of connections are supported (can handle 127 devices)

Question 23

USB vs USB drive

Answer 23

• USB drive - the portable storage device
• USB is the medium by which it connects to a device

Question 24

VGA port

Answer 24

Is a different port e.g. used for a second monitor
+High resolution screen display suitable for most display requirements
- Does not transmit audio - hence HDMI is needed

Question 25

HDMI port

Answer 25

provide a connection to a screen and allow the transmission of high-quality video and audio
+ has audio

Question 26

FDE cycle

Answer 26

PC points to next address
address stored in MAR
data from that address stored in the MDR
data then transferred to the CIR and decoded by the CU - the instruction is then executed and the PC increases by 1

Question 27

register transfer notation

Answer 27

• The format is: Destination ← [source]
• destination = register
• destination ←[[MAR]] - double brackets mean its the contents of that address which is transferred to the destination
• two data operations placed on the same line separated by a semi-colon - means that the two transfers take place simultaneously

Question 28

reasons fro interrupts

Answer 28

• fatal error in a program
• a hardware fault
• a need for I/O processing to begin
• user interaction
• a timer signal.

Question 29

handling interrupts

Answer 29

• contents of PC and registers are stored in memory
• the appropriate ISR (Interrupt Service Routine) program is initiated by loading its start address to PC
• immediate check to see if further interrupts need handling
• further interrupts are dealt with by repeated execution of the ISR program.
• If no further interrupts, the contents of the registers are restored to CPU and program is resumed