Unit 5 - Computer Organisation and Architecture Flashcards
(138 cards)
1
Q
What is a computer system?
A
Any system that can take a set of inputs and process them to produce useful outputs
2
Q
Why is an I/O controller required in a computer?
A
This is necessary because the processor cannot communicate directly with peripheral devices
3
Q
How does the I/O controller work?
A
The I/O controller converts the signals sent by the peripherals into a format which the processor can understand and vice versa
4
Q
What piece of software works in unison with the I/O controller?
A
A device driver
5
Q
What does the device driver do?
A
A device driver is a piece of software that allows peripheral devices to communicate with the processor. The component of the processor is communicates with is the I/O controller.
6
Q
Busses are made up of _______
A
Microscopic parallel wires
7
Q
What are the 4 standard bus sizes
A
8, 16, 32 or 64 lines
8
Q
T/F: the control bus is omnidirectional
A
True
9
Q
What does omnidirectional mean?
A
Signals can be sent in both directions
10
Q
What is the control bus used for?
A
Controls the flow of data between the processor and other parts of the comput
11
Q
T/F: you can only send signals in one direction on the data bus
A
False: the data bus is omnidirectional
12
Q
What impact will increasing the width of the data bus have on the computer?
A
It will increase the performance of the computer because the more wires there are in the data bus the more bits can be sent at once
13
Q
Which two busses are omnidirectional?
A
The control and data bus
14
Q
Which bus is unidirectional?
A
The address bus
15
Q
What is the address bus used for?
A
It sends memory addresses from the processor to CPU components
16
Q
What does the width of the address bus determine?
A
The maximum number of memory addresses of that system because a memory address is sent in one operation
17
Q
What are the 5 main control signals?
A
- Memory read
- Memory write
- Bus request
- Bus grant
- Clock
18
Q
What do the control signals memory read and memory write do?
A
Memory read causes data from the addressed location to be placed on the data bus
Memory write causes data from the data bus to be written into the addressed location
19
Q
What do the control signals bus request and bus grant do?
A
Indicates that a device is requesting use of the data bus
Indicates that the CPU has granted a device access to the data bus
20
Q
What does the control signals clock do?
A
Synchronises operation
21
Q
What is the word length?
A
The number of bits that can be addressed, transferred or manipulated as one unit
22
Q
What is stored in main memory?
A
Data and instructions
23
Q
What is a general purpose computer?
A
A computer that can perform many different tasks at different times
24
Q
What is the fixed program concept?
A
This described the programming of early computer when they only had one program which meant that they could only do one thing
25
What is the stored program concept?
The idea that instructions are stored together in main memory so they can be accessed easily by the processor
26
What is the difference between Von Neumann and Harvard architecture?
In the von Neumann architecture instructions and data are stored in the same memory where as they have different memories in the Harvard architecture
27
T/F: the von Neumann architecture is viewed as better than the Harvard architecture
False: the Harvard architecture is viewed as superior because it allows for different word lengths and memory capacity for the two different types of information
28
Why is the von Neumann architecture more commonly used?
The Harvard architecture is more costly and is very complex to program as well as requiring more physical space
29
What happens during the Fetch-Decode-Execute cycle?
1. Address of next instruction transferred from PC to MAR
2. PC incremented by 1
3. Instruction stored in location addressed by MAR is transferred to MBR
4. Instruction transferred from MBR to CIR
5. Instruction in the CIR gets decoded by the CU and split into the opcode and operand
6. Additional data, if required by the instruction, is fetched from the memory
7. Additional data passed to registers
8. Instruction executed by the ALU
9. Registers are used to store intermediate data or results
10. Result is stored in the accumulator or general purpose register or memory
30
What are the 6 main dedicated registers and their purpose?
Program Counter: holds the memory address of the next instruction to be executed, located in the CU
Current Instruction Register: holds the instruction that is currently being decoded or executed
Memory Address Register: Holds the address of the memory location that the processor has to fetch or store data from or in
Memory Buffer Register (aka Memory Data Register): Temporarily holds data moving between the processor and main memory
Status Register: holds information about the current state of operations, sets flags and detects error conditions
Interrupt register: Stores details of incoming interrupts
31
What factors effect the performance of a computer system?
Clock speed, cache memory, number of cores, word length and address and data bus width
32
What are the sub-components of the processor?
ALU, CU, Clock, General Purpose Registers and Dedicated Registers
33
What does the processor do?
Controls, calculates and executes instructions
34
What does the ALU do?
Performs, arithmetic, logic and sift operations and acts as the problem-solving component within the processor
35
What does the CU do?
Coordinates and organises the processor through the utilisation of the fetch-decode-execute system and synchs each step with a pulse from the clock
36
What do general purpose registers do?
Temporarily stores results from the ALU before they need to be used
37
What is the accumulator?
A replacement for the general purpose registers, it is a register that it specifically for temporarily storing results from the ALU
38
What do dedicated registers do?
Hold specific data
39
What does the clock do?
Synchronises when instructions are executed, it controls the speed at which the processor works. Instructions are generally executed on the rising edge of the clock and different instructions will take a different number of cycles to complete.
40
What is an instruction set?
The different commands which the processor can perform
41
Why do different processors have different instruction sets even if they perform the same instructions?
They have different ways of expressing instructions
42
What are the 6 different types of instruction?
1. Data transfer .e.g. LOAD or STORE
2. Arithmetic operations .e.g. ADD or SUBTRACT
3. Comparison operations
4. Logical operations .e.g. AND, OR or NOT
5. Branch, conditional and unconditional
6. Shift operations, shifting bits left and right
43
What language does the processor understand?
Machine code
44
What are the two parts of an instructions?
The opcode and the operand
45
What is the opcode?
The section of the instruction which dictates the command which the processor must execute
46
What is the operand?
The section of the instruction which provides the information the processor is to use to execute the command given in the opcode
47
What is immediate addressing?
This is when the information to be used in the command is given in the operand
48
What is direct addressing?
This is when the memory address of the data to be used in the command in given in the operand
49
What is the addressing mode?
The section of the opcode (often two bits) which indicates what type of addressing the command is using and whether it is immediate or direct
50
What method of expressing information does assembly language use?
Mnemonics
51
What section of the instruction does the mnemonic represent in assembly language?
The opcode
52
What character is used to indicate a comment in assembly language?
;
53
What type of storage is volatile?
Primary storage
54
What type of storage is non-volatile?
Secondary storage and Main Memory
55
Define processor
A device that carries out computation on data by following instructions in order to produce an output
56
Give the simplest explanation of main memory?
Stores data and instructions that will be used by the processor
57
What is a chip?
An electronic component contained within a thin slice of silicon
58
What physical component make up RAM?
Chips
59
What physical component comprises the RAM?
A thin slice of silicon implanted with millions of transistors that are connected by busses
60
What do transistors do?
Control the flow of electrical pulses that are sent in time with the clock
61
What is another name for ROM?
Main Memory
62
Where are the instructions for computer start up stored?
ROM
63
What is the difference between RAM and ROM?
1. ROM cannot be written to unless it is programmable ROM where as RAM can
2. RAM is volatile meaning it will not store any information once the computer is switched off whereas ROM does
64
What is addressable memory?
Memory made up of millions of addressable cells that each have a unique identifier
65
Why is it beneficial for the width of the data bus to be the same as the word length of the computer?
All data units can be sent in one operation
66
What is the memory word length?
The smallest unit of addressable memory in a computer system
67
What two components does the address bus connect?
Main memory and the processor
68
Describe the concept of addressable memory
The concept that data and instructions are stored in memory using discrete addresses
69
What is the role of physical ports on a computer?
They allow I/O devices to be connected
70
What is the I/O controller an example of?
An interface
71
What are the two roles of an I/O controller?
They translate signals from peripheral devices into the format required by the processor and act as a buffer for data being sent from the device to a the processor as it works at a much slower speed than the processor
72
What does the word architecture refer to in computer science?
The way in which something is built
73
What is the hardware difference between the von Neumann and Harvard architecture?
The way in which the chip is constructed
74
What type of computer system is the Harvard architecture more commonly used on?
Embedded systems .e.g. mobile phones or burglar alarms
75
What is digital signal processing?
DSP is a process that takes continuous real world data and compresses it to allow for faster processing
76
Why are chips optimised for DSP often used in mobile phones?
They have low power consumption which is necessary for mobile phones
77
Describe the fetch section of the fetch-execute cycle in one sentence
The processor retrieves the program's next instruction from an addressable memory slot which will be in machine code
78
Describe the decode section of the fetch-execute cycle in one sentence
The processor determines what the machine code instruction is telling it to do
79
Describe the execute section of the fetch-execute cycle in one sentence
The processor will carry out the instruction
80
How does the clock speed affect the performance of a processor?
It determines the number of clock cycles that occur per second which affects the number of instructions that are be executed by the processor per second
81
How does the bus width affect the performance of a processor?
The width of the data bus dictates how many bits can be sent in one operations and the width of the address bus dictates the number of addressable memory locations
82
How does the word length affect the performance of a processor?
The word length dictates the maximum number of bits that can be manipulated with one pulse of the clock
83
How does the number of cores affect the performance of a processor?
The term core defines the components that allow the fetch-execute cycle to occur so having multi-core system means you have more than one processor on one chip which means that more instructions can be executed per second
84
How does the cache memory affect the performance of a processor?
Cache memory can be accessed by the processor much faster than main memory can be so having more information stored in the cache memory means reduced latency when the processor wants to retrieve information
85
What is an interrupt?
A signal sent by a device or program to the processor requesting its attention
86
How does the processor check for an interrupt?
Between the end of each fetch-execute cycle and the start of the next the processor checks the contents of the interrupt register to see whether an interrupt has been sent
87
What does the processor do if an interrupt has been sent?
1. The processor pushes the current contents of the registers onto the system stack
2. It will the look up what type of interrupt it is and the associated vector
3. The processor will jump to the address specified by the vector
4. The ISR will be run
88
What is the Interrupt Service Routine (ISR)?
This is a routine which determines which routine is necessary to deal with the interrupt and then calls it (some are provided by device drivers for peripheral interrupts)
89
How does the processor handle its current task when an interrupt is sent?
It pushes the current contents of the registers onto the system stack until the interrupt has been dealt with when it will pop them again and place them back in the appropriate registers to resume
90
How does the processor deal with one or more interrupts at once?
It will assess the interrupts to determine which is more important and then deal with that one first .e.g. a printer will deal with an interrupt saying it is about to lose power before an interrupt saying that it is out of paper
91
What is a vectored interrupt mechanism?
A method of handling interrupts by pointing to the first memory address of the instructions needed
92
Describe why a vectored interrupt mechanism is necessary
Each interrupt has an associated memory address known as a vector that points to the starting address of the code associated with each interrupt in order for it to be run to deal with the interrupt
93
Describe how a camera works
1. The shutter opens and light is allowed to enter the lens
2. The light is focussed by the lens through RGB filters to define colour
3. Light is focussed on a sensor which is either a CCD or a CMOS
4. The sensors consist of millions of transistors and each one holds data for one or more pixels
5. As light hits the sensor it is converted to electrons and the amount of charge is recorded for each pixel
94
What is a CCD?
Charge coupled device - a sensor in digital cameras that records the amount of light received and converts it into a digital value
95
What is a CMOS?
Complementary Metal Oxide Semiconductor - a sensor in digital cameras that records the amount of light received and converts it into a digital value
96
How do you define the capability of a digital camera?
You define a camera's capabilities in terms of the number of megapixels that it uses to record images
97
Define compression
The process of reducing the size of a file
98
Define resolution
The number of pixels used to create an image
99
What is a barcode reader?
A device that uses lasers or LEDs to read the black and white lines of a barcode
100
How does a barcode scanner work?
1. A light is passed over the barcode
2. A sensor (such as a CCD or photodiode) measures the intensity of light being reflected back which is converted into current
3. The waveform will represent the black and white areas of the barcode because they will reflect different amounts of light
4. The waveform is converted from analogue into a digital binary representation
5. This binary representation can then be interpreted by the software
101
What is a UPC and how does it work?
Universal product code - has a series of black lines that can be 4 different widths and are encoded to represent the values 1 to 4. They also have numbers underneath them which are used as a manual override and include a check digit.
102
How do EAN barcodes work for identifying food items?
EAN stands for European Article Number and each barcode number is present in a POS (point of sale) database that is used to identify the item
103
T/F: QR codes are an iteration of barcodes
True
104
How do QR codes differ from barcodes?
They consist of black and white blocks rather than lines, they can be read by a smartphone and can contain a wider range of information
105
What is an RFID?
A microscopic device that stores data and transmits it using radio waves
106
What is the most common use of an RFID?
Tracking items
107
Describe how an RFID works
1. The tag contains a chip which contains data about the item, a modem which modulates and demodulates the radio signals and an antennae
2. Tags are either active or passive
3. Tags can then receive and transmit signals
108
Describe the logical difference between an active and a passive RFID
An active RFID will allow the user to always identify the location of the tag where as a passive RFID only allows the tag to be used when it is range of the RFID reader
109
Describe the physical difference between an active RFID tag and a passive RFID tag
An active RFID tag has its own power source which is usually in the form of a small battery whereas a passive RFID tag uses electromagnetic waves transmitted by the reader as a power source
110
What is the typical range of an RFID tag?
1m - 100m
111
Give some real world examples of the applications of RFID tags
1. Tracking individuals
2. Electronic passports
3. In cards to enable contactless payments
4. School lanyards for singing in and out
5. Tracking shipments and individuals
6. Used to keep track of high value items in case they are stolen
112
What is a laser printer?
A device that uses lasers and toner to create monochromatic and colour prints
113
Describe how a laser printer works
1. A rotating drum in the printer is coated with a chemical that has a negative charge
2. A laser beam is reflected onto the drum and it discharges the area it is focussed on
3. As the drum rotates it picks up toner which is attracted to the charged part of the drum
4. Paper is passed over the drum and the toner is then attracted from the drum to the paper as it has an opposite charge
5. Heat is used to fuse the toner to the paper
114
How does a colour printer vary from a monochromatic printer?
A colour printer uses four different shades of toner which are cyan, yellow, magenta and key (black)
115
What is a hard disk (HDD)?
A secondary storage device that us made up of metallic disks that store data magnetically
116
Why are hard disks hermetically sealed?
To prevent the disks from being corrupted by dust or debris
117
What is the physical composition of a hard disk?
There are several disks arranged in a stack with each having a read write head above it. The disks rotate and the heads move laterally meaning they can access any part of the disk
118
How is storage on a hard disk organised?
The hard disk is split into sectors, each of which can be referenced by the OS. The sectors are arranged in concentric circles called tracks. The OS also groups sectors together into clusters which makes them easier to organise.
119
What happens if a file only needs part of a cluster?
It will be allocated the whole cluster to make storage easier to organise
120
What is the downside to clusters?
Because files will be allocated a whole cluster even if they don't need it hard disks often have redundant space on them
121
How do the heads read and write data from a hard disk?
The hard disk is coated in a magnetic coating which has areas of varying magnetism. A change in the direction of magnetism can be read as 1's and 0's
122
What is the speed of a hard disk?
3600-12500rpm
123
What is the typical capacity of a hard disk?
1Tb
124
How does a read only optical disk work?
The disk has one track that starts in the middle and works its way to the edge in a series of concentric circles. The track consists of a series of pits and lands that are coated with a protective layer and a sensor reads how much light is reflected from the disk. This means that a laser is shone on the track of the disk and a pits of lands reflect light back to the sensor but a transition reflects the light so it misses the sensor. The amount of light reflected is read as an electrical signal and is then converted to binary
125
How is a writeable optical disk constructed?
The disk is coated with a photosensitive dye that is translucent
126
How do you write data to a writeable optical disk?
A laser alters the state of different dye spots by changing their density so that they become opaque
127
How do you read data from a writeable optical disk?
A read laser reads the density of different areas on the optical disk based on the amount of light they reflect and these readings are interpreted as 1's and 0's
128
What is a controller in an SSD?
The component that is needed to organise data into blocks for storage purposes
129
What is a block in an SSD?
The concept of storing data into set groups of bits that have a fixed length
130
What is a floating gate transistor?
A type of non-volatile transistor that stores data even without a power source
131
How does an SSD work?
An SSD consists of programmable ROM chips that contain NAND memory. This means that it has blocks of NAND memory cells that consist of floating gate transistors which trap charge that is then interpreted as a 1 or a 0
132
How does a floating gate transistor work?
It consists of two gates which are the floating gate and the control gate. The gates have an oxide between them which traps the charge even when the power is off.
133
What are the advantages of SSDs?
The blocks means that it is very easy for the controller to locate specific memory cells and it also has a low latency because of this. They also have lower power consumption, are silent in operation and are not susceptible to damage. They also have less chance of mechanical failure than HDDs and their performance does not degrade over time as they do not require defragmentation.
134
Detail the arrangement of data on a hard disk
Blocks contain fixed amounts of binary data. The blocks are then allocated to particular semiconductors in the disk. The semiconductors consist of floating gate transistors which hold the charge the represents the binary values in the blocks.
135
Rank the three forms of secondary storage on latency
Low - SSD
High - HDD and optical disk
136
Rank the three forms of secondary storage on capacity
High - HDD
Medium - SSD
Low - optical disk
137
Why does clock speed have a limit?
Overclocking can cause the processor to overheat
138
Define clock speed
The number of clock cycles performed per second (not the number of instructions because some instructions may take more than one clock cycle to complete)
