4.7 Fundamentals of computer organisation and architecture Flashcards
(77 cards)
1
Q
What is the role of a processor
A
executes program instructions to run applications
2
Q
what is main memory
A
includes RAM and ROM to store program instructions and frequently used data, this is usually faster than secondary storage
3
Q
what is a bus
A
a series of parallel wires that connect internal components - allows signals to pass between the processor and them
4
Q
I/O controller
A
input / output controllers are hardware pieces that control communication of data between the processor and external hardware e.g keyboards
5
Q
what is the width of a bus
A
number of parallel wires
6
Q
what is the width of a bus related to
A
number of bits that can be transferred simultaneously
7
Q
What is the address bus
A
it is a unidirectional bus that transports memory addresses, it specifies where data is sent and received from
8
Q
what is the result of increasing the width of the address bus
A
increases the range of addresses that can be specified so it increases the computer’s amount of addressable memory - adding a wire doubles the number of addressable memory locations
9
Q
what is the data bus
A
it is a bidirectional bus that sends data and instructions to and from different components
10
Q
what is the result of increasing the width of the data bus
A
increasing width increases the volume of data that can be transferred at a time
11
Q
what is the control bus
A
carries control signals that regulate the operation of the computer system such as carrying clock signals
12
Q
describe the von Neumann architecture
A
both instructions and data are stored together in memory, tends to perform worse as the same buses have to be shared for data and instructions
13
Q
where is the von Neumann architecture typically used
A
used for everyday general-purpose computer systems like laptops or smartphones
14
Q
describe the Harvard architecture
A
the processor uses two separate main memory locations, one for instructions and one for data - this means that each main memory can have different characteristics eg read only for instructions
15
Q
where is Harvard architecture typically used
A
embedded systems such as digital signal processing
16
Q
what is the concept of addressable memory
A
each memory location in a computer has a unique address, allowing the CPU to read from or write to specific locations in memory directly
17
Q
describe the stored program concept
A
machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations
18
Q
what is the role of a processor
A
to execute instructions by performing basic arithmetic, logic, control, and input/output operations
19
Q
what does the arithmetic logic unit do
A
performs arithmetic and logic operations
20
Q
what does the control unit do
A
controls the various components of the processor
21
Q
what does the clock do
A
a device that generates a timing signal which changes at a regular frequency - used to synchronise communication between processor components and the rest of the computer system
22
Q
what are registers
A
they are small storage locations used to hold data temporarily
23
Q
what is a general purpose register
A
used as storage for any data that is required by instructions during execution
24
Q
what are special purpose registers and name them
A
registers assigned to the storage of specific information - PC, CIR, MAR, MBR, SR
25
what does the PC register do
Program Counter register holds the memory address of the next instruction to be executed
26
what does the CIR register do
Current Instruction Register holds the instructions that is currently being executed by the processor
27
what does the MAR register do
Memory Address Register stores the memory address of the location to be read from or written to
28
what does the MBR register do
Memory Buffer Register holds the contents of a memory location that has been read from or data that is to be stored
29
what does the SR register do
Status Register contains a number of bits which the value can change to indicate an interrupt
30
when to check for interrupts in a fetch execute cycles
between the execute and fetch stage
31
what are the steps that the computer does in the fetch stage
1) contents of PC is copied to the MAR
2) content of the MAR is transferred to the main memory via address bus
3) the instruction is sent from the main memory to the MBR by the data bus
4) the PC is incremented by one
5) the content of the MBR is copied to the CIR
32
what are the steps that the computer does in the decode stage
1) the content of the CIR is decoded by the control unit
2) the decoded instruction is split into two parts : opcode and operand
33
what are the steps that the computer does in the execute stage
1) any data required by the instruction that isn't present in registers is fetched
2) the instruction is carried out
3) results of any calculations are stored in general purpose registers or main memory
34
what is the processor instruction set
complete set of instructions that a processor can execute, including operations like arithmetic, data movement, and control flow
35
what are the two parts of an instruction
first part - opcode - specifies the type of operation to be carried out
second part - operand - pieces of data which the data is performed on
36
what are the types of operands
the operand can either be a value or the memory address of the data to be used
37
what does the last bit of the opcode represent
the addressing mode
38
what are the two addressing modes and what do they mean
immediate - the operand is the numerical value it represents
direct - the operand indicates a memory address of where to retrieve the data needed for the operation
39
what is an interrupt
a signal sent to the processor by another part of the computer requesting the attention of the processor
40
examples of hardware and software sending interrupts
hardware - mouse clicks or keys pressed on keyboards
software - errors such as division by zero and stack overflow
41
what happens when an interrupt occurs
contents of status register is changed
42
how are interrupts handled
with the 'vectored interrupt method' - processor stops executing current program and places the contents of its current registers onto the system stack (known as saving the volatile environment) - after this it loads the appropriate interrupt service routing which are instructions to handle specific interrupts - when the processor finished executing the interrupt service routing it restores the volatile environment from the system stack and resumes the execution of the previous program
43
what are the factors that affect processor performance
multiple cores, cache memory, clock speed, word length, address bus width, data bus width
44
how does the number of cores affect the processor performance
since each core performs independently, more tasks can be executed at the same time, so having more cores improves the processor performance through better multitasking
45
how does the cache memory affect the processor performance
cache memory improves processor performance by storing frequently used data and instructions close to the CPU, reducing the time it takes to access them compared to fetching from main memory
46
how does the clock speed affect the processor performance
clock speed affects processor performance by determining how many instructions the CPU can execute per second; a higher clock speed means the processor can perform more operations in less time
47
how does the world length affect the processor performance
word length affects processor performance by determining how much data the CPU can process at once and the size of memory addresses it can use; a larger word length allows for faster processing and access to more memory
48
how does the address bus width affect the processor performance
the address bus width affects processor performance by determining how much memory the CPU can directly address; a wider address bus allows access to more memory, which can improve performance in memory-intensive tasks
49
how does the data bus width affect the processor performance
the data bus width affects processor performance by determining how much data can be transferred to and from the CPU in one operation; a wider data bus allows more data to be moved at once, increasing processing speed
50
main characteristics of barcodes
barcodes are printed diagrams that consist of light and dark portions
51
difference between 1D and 2D barcodes
2D barcodes contain more information in the same space as a 1 barcode but it required more processing in order for the information to be extracted
52
how do barcode readers work
they consist of a laser light source, a lens, photodiodes and a mirror - the mirror directs the light from the laser onto a printed barcode - the light reflected by the barcode passes through the lens and is incident on the photodiode which turns light into electrical charge - this electrical charge can be measured and processed to form a digital signal representing the content of the barcode - light portions of a barcode reflect the most light while dark sections absorb incident light - the pattern of light and dark stripes corresponds to binary 1s and 0s
53
what error detection does barcodes have
they parity bits and check digits to tell whether a barcode has been read correctly - if a barcode fails to scan correctly it will continue to scan until correct - barcode readers can scan barcodes 1000s of times a second do delay by rescanning is imperceptible to humans
54
how do digital cameras work
digital cameras consist of a lens that focuses light onto a sensor, the path of light between the lens and the sensor is regulated by a shutter - two sensors used are CMOS (complementary metal oxide semiconductor) and CDD (charge coupled device) both convert incident light into electrical charge - charge builds up in cells each of which represents a pixel in the image - when the photo is taken the charge in each cell is measured and converted into a digital value which is then processed and stored as a digital image
55
what differs for a colour camera
there are multiple cells for each pixel, each of which has a filter that only allows in a certain wavelength of light - this lets camera build up a separate image for the intensity of each colour of light which can be combined to form a full colour
56
what is a bayer filter
a special colour filter used in digital cameras that has the same number of green filters as red and blue combined - this produces an image that is a close approximation of what the human eyes see which are most sensitive to green light
57
how do laser printers work
laser printers consist of a laser light source, a mirror, a drum, a toner roller and fusers - when a document is printed, the drum is positively charged before the laser is directed at its surface by the mirror, areas where the laser is incident become discharged leaving an impression of the page on the drum - the toner roller dispenses negatively charged toner onto the drum and because opposite charges attract the toner is attracted to the positve portions of the drum - the toner then applied to the paper by the drum before the paper is heated, fixing the toner to the paper
58
what is different for colour printers
they apply the same process with four different colours of toner - cyan, yellow, magenta and black
59
what is RFID and what is its purpose
radio frequency identification - method of transferring information wirelessly between a tag and reader - used in contactless credit and debit cards
60
what is inside an RFID tag
there is a chip which contains a small amount of memory, the chip is attached to a coil of wire that acts as an antenna
61
what happens when an RFID tag is scanned
the reader emits radio waves which are picked up by the tag's antenna, the power induced in the tag's antenna from these waves is enough to power the chip, which then uses its antenna to emit its own radio wave which contains the information held on the chip, this wave is picked up by the reader which decodes the information and returns the information to the computer
62
What is the need for secondary storage within a computer system
secondary storage is needed to store data and programs permanently, as primary memory (RAM) is temporary and loses data when the computer is turned off. It provides long-term, non-volatile storage
63
what do hard disk drives consist of
a number of circular platter which are made from magnetic material, above each platter hovers an actuating arm on which is a read/write head
64
how do hard drive disks work
the actuating arm allows the read/write head to access all portions of the platter and change the magnetic polarity of the platter - data is written in concentric tracks, each of which is further divided into sectors
65
how to keep hard disk drives the same size by increase their capacity
adding more platters and decreasing the width of the tracks
66
what do solid-state drives consist of
NAND flash memory cells and a controller that manages the structure of data on the drive
67
characteristics of solid-state drives
NAND flash memory is non-volatile, meaning that an SSD's contents are retained even when there is no power being supplied - the memory cells are formed of floating gate transistors which store information by trapping electrical charge - SSDs are not capable of overwriting data so the controller must completely erase the entirety of a page before writing new information to it
68
what do optical disks consist of
there are pits burned into the disk by a high-power laser which permanently deforms the surface and lands are the areas that surround them - they have one continuous track which spirals from the centre to the outside edge
69
how do optical disks work
when a low-power laser beam is passed over the surface, it reflects back onto a photodiode, however when the laser is incident on a pir the light from the bream is scattered, the resulting pattern of reflections and scatters can be converted into digital signals of binary 1 and 0
70
whats the difference on recordable and rewriteable optical disks
a pattern of reflections and scatters is created by dye on the disks surface - recordable disks uses photosensitive dye that changes from opaque to transparent under a high power laser - rewritable optical disks use a different type of dye that can be converted multiple times between transparent and opaque changing state depending on temperature heated to
71
compare typical capacity between hard disk drives, solid state drive and optical disk
hard disk drive - high between 500GB and 5TB
solid-state drive - low under 1TB
optical disk - very low under 25GB
72
compare read/write speeds between hard disk drives, solid state drive and optical disk
hard disk drive - good at 100MB/s
solid-state drive - very high at 500MB/s
optical disk - low at 30MB/s
73
compare latency between hard disk drives, solid state drive and optical disk
hard disk drive - high
solid-state drive - very low
optical disk - high
74
compare portability between hard disk drives, solid state drive and optical disk
hard disk drive - bad cause bulky and heavy and easily damaged by movement
solid-state drive - good cause lightweight and rarely damaged by movement
optical disk - ok cause very small and lightweight by damaged by scratches and dirt
75
compare power consumption between hard disk drives, solid state drive and optical disk
hard disk drive - high
solid-state drive - low
optical disk - high
76
compare stability between hard disk drives, solid state drive and optical disk
hard disk drive - good for desktop PCs and servers
solid-state drive - good for laptops phones and tablets
optical disk - good for sharing small volumes of data
77
what is latency on secondary storage
Latency on secondary storage is the delay between requesting data and the start of data transfer. It includes the time taken to locate and access the data on the storage device.
