Section 5: Computer Organisation and Architecture Flashcards
Chapter 25:
What are the three main busses in a computer?
Control Bus.
Data Bus.
Address Bus.
Chapter 25:
What are the six main components of the CPU?
Control Unit. (CU) Arithmetic Logic Unit. (ALU) Registers. Cache. Busses. Clock.
Chapter 25:
What does the Control Unit do?
Coordinates and Controls all operations carried out by the computer.
Follows the Fetch-Decode-Execute Cycle.
Chapter 25:
What does each stage of the Fetch-Decode-Execute Cycle do?
Fetch:
Causes the next instruction to be fetched from main memory.
Decode:
Decodes the instruction.
Execute:
Runs the instruction.
Chapter 25:
What are the two types of operation that the ALU can perform?
Arithmetic.
Logical.
Chapter 25:
What are Arithmetic operations in the ALU?
Deal with values.
Add.
Subtract.
Multiply.
Divide.
Chapter 25:
What are Logical operations in the ALU?
Deal with comparisons and switches.
NOT. AND. OR. XOR. NAND. NOR. XNOR. Buffer. & Shifts.
Chapter 25:
What are Registers?
Memory cells that operate at very high speeds, due to the small distance to travel; being inside the CPU.
Chapter 25:
What is a bus (in a computer)?
A set of parallel wires (“lines”) connecting two or more components of a computer.
Speed measured in Megahertz (MHz).
Chapter 25:
What do the Address Bus, Data Bus, and Control Bus do?
When the CPU wants to access a particular memory location, a signal is sent down the Address Bus to the main memory.
The data will then be transferred either from Memory to the CPU, or from the CPU to Memory. The data is transferred across the Data Bus.
The Control Bus carries commands to, and status reports from other hardware devices. The Control Bus also carries Clock Pulses, which help to keep the system under control and stop conflicts (queue transfers).
Chapter 25:
What is the “size” or “width” of a bus?
How many bits can be transferred at once. (How many lines it has)
64-bit computers have 64-bit bus widths.
Chapter 25:
A Bus is a collection of wires. What are these wires called?
Lines.
Chapter 25:
Are the following busses Unidirectional or Bidirectional?
Address Bus, Data Bus, Control Bus
Address Bus = Unidirectional.
Data Bus = Bidirectional.
Control Bus = Bidirectional.
Chapter 25:
What are Address Busses, Data Busses, and Control Busses known collectively as?
The System Bus.
Chapter 25:
What is a transmission medium?
Give an example of a transmission medium in a computer?
Where something can mediate the propagation of signals. (Sync signals to avoid collisions).
Busses are an example.
Chapter 25:
Control Busses have 7 Control Signals. List them.
Memory Write: causes data on the data bus to be written to a specified location.
Memory Read: causes data from a specified location to be placed into the data bus.
Interrupt Request: indicates that a device is requesting access to the CPU.
Bus Request: indicates that a device is requesting access to the Data Bus.
Bus Grant: indicates that the CPU has granted access to the Data Bus.
Clock Pulse: used to synchronise operations.
Reset: initialises all components.
M(WR) I B(RG) C R
Chapter 25:
How does the width of the Data Bus effect the overall system performance?
Data Bus is typically made of 8, 16, 32, or 64 lines.
When a 64-bit instruction needs to be sent down a 32-bit Data Bus, the instruction needs two calls to be sent.
This involves splitting the instruction up, as well as sending double the transmissions.
Chapter 25:
Memory is divided up internally into units.
What are these units called?
Typically how large are they?
Words.
Typically 8, 16, 32, or 64 bits in size.
Different CPUs use different sizes.
Chapter 25:
Which System Bus determines the maximum possible memory capacity of a computer system?
Why?
The Address Bus.
The Address Bus cannot map one combination of its bits to more than one memory location.
Chapter 25:
What is the maximum theoretical memory capacity of a 64-bit PC?
16,777,216 TiB (Tebibytes)
2^64 (B) /1024 (KiB) /1024 (MiB) /1024 (GiB) /1024 (TiB)
Chapter 25:
What is the maximum theoretical memory capacity of a 32-bit PC?
4 GiB (Gibibytes)
2^32 (B)
/1024 (KiB)
/1024 (MiB)
/1024 (GiB)
Chapter 25:
What is an I/O controller?
A device that interfaces between an input or output device, and the CPU.
I/O controllers are unique to the input/output device.
Chapter 25:
How does an I/O controller connect to the CPU?
Via the control bus.
Chapter 25:
How are instructions send from the CPU, through the I/O controller, into the device?
CPU sends and input/output request to the I/O controller.
The I/O controller receives this, and sends device-specific control signals to the device. It also manages the data flow to and from the device.
Chapter 25:
What are the three main parts to an I/O controller?
An interface that connects the controller to the device system.
A set of data, command, and status registers.
An interface that connects the controller to the computer’s CPU.
Chapter 25:
What is an interface?
A standardised form of connection defining such things as signals, number of connecting pins/sockets, and voltage levels
Chapter 25:
What is an example of an interface?
Universal Serial Bus (USB)
Chapter 25:
What is the stored program concept?
Machine Code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations.
Chapter 25:
What makes Von Neumann’s design special?
Data and Instructions are stored as binary in the same memory.
Chapter 25:
Other than Von Neumann Architecture, what is the other common CPU Architecture used?
Harvard Architecture.
Chapter 25:
What is the main difference between Von Neumann Architecture and Harvard Architecture?
In Von Neumann Architecture, Data and Instructions are stored in the same memory.
In Harvard Architecture, Data and Instructions are stored in different memories.
Chapter 25:
What is DSP?
Digital Signal Processing.
Take a Digital Signal, Process (adapt) it into a different one.
Often used to improve the sound quality of an audio file.
Chapter 25:
What are advantages to Harvard Architecture?
Where is it used?
Can be faster, as Data and Instructions can be fetched in parallel, rather than competing for the same bus.
Used often in Digital Sound Processing (DSP).
Chapter 25:
What are disadvantages to Harvard Architecture?
Having multiple data busses and memories comes with cost.
Increased Hardware complexity.
Can execute some instructions slower.
Chapter 25:
What direction are the connections between the Address Bus and the following components?
Processor, Main Memory, Keyboard Input Controller, VDU Output Controller, Disk I/O Controller.
AB from Processor, AB to Main Memory, AB to Keyboard Input Controller, AB to VDU Output Controller, AB to Disk I/O Controller.
Chapter 25:
What direction are the connections between the Data Bus and the following components?
Processor, Main Memory, Keyboard Input Controller, VDU Output Controller, Disk I/O Controller.
Data Bus to&from Processor, Data Bus to&from Main Memory, Data Bus from Keyboard Input Controller, Data Bus to VDU Output Controller, Data Bus to&from Disk I/O Controller.
Chapter 25:
What direction are the connections between the Control Bus and the following components?
Processor, Main Memory, Keyboard Input Controller, VDU Output Controller, Disk I/O Controller.
Data Bus to&from Processor,
Data Bus to&from Main Memory,
Data Bus to&from Keyboard Input Controller,
Data Bus to&from VDU Output Controller,
Data Bus to&from Disk I/O Controller.
Chapter 26:
What are the components of the CPU?
Control Unit (CU) Arithmetic Logic Unit (ALU) The System Clock General-purpose registers Dedicated registers
Cache
Busses
Chapter 26:
What does the Control Unit do?
Controls and coordinates the activities of the CPU, directing the flow of data between the CPU and other devices.
Accepts the next instruction, breaks it down, into sequential steps, manages the execution, and stores the resulting data back into memory or registers.
Chapter 26:
What does the System Clock do?
Generates a pulse, switching between 0 and 1 billions of times per second.
All CPU operations are synced to these pulses.
Chapter 26:
What is a System Clock pulse?
Where the clock value changes from 0 to 1, or 1 to 0 (depending on the CPU) .
This happens billions of times per second.
3 GHz clock = 3 Billion pulses per second.
Chapter 26:
What is a general-purpose register?
Small storage located inside the CPU.
They store the results of arithmetic and logical operations from the ALU.
There are typically 16 registers in a CPU ( R0, R15 ).
Chapter 26:
What format does the CPU follow to execute instructions?
The Fetch-Decode-Execute Cycle.
Also known as the Fetch-Execute Cycle.
Chapter 26:
What are the 6 main Dedicated Registers?
Also known as Special-purpose Registers:
Program Counter. (PC)
Current Instruction Register. (CIR)
Memory Address Register. (MAR)
Memory Buffer/Data Register. (MBR)/(MDR)
Status Register. (SR)
Accumulator. (ACC) (Often considered general-purpose)
Chapter 26:
What happens during the Fetch stage of the Fetch-Decode-Execute Cycle?
- The Address of the next instruction, stored in the Program Counter, is copied over to the Memory Address Register. From here, the Address is sent down the Address Bus to main memory.
- The instruction held at that Address is returned along the data bus to the Memory Buffer/Data Register.
The content of the Program Counter is also incremented to prepare for the next instruction. - Content of the Memory Buffer/Data Register is copied over to the Current Instruction Register.
Chapter 26:
What happens during the Decode stage of the Fetch-Decode-Execute Cycle?
- The instruction in the Current Instruction Register is sent to the Decode Unit, where it is split into opcode and operand, and returned to the CIR.
Additional Data is Fetched if required.
Chapter 26:
What happens during the Execute stage of the Fetch-Decode-Execute Cycle?
- The instruction is Executed, using the ALU if required.
Results are stored in the Accumulator, general-purpose registers, or main memory.
Chapter 26:
When is the Program Counter NOT incremented by 1 in the Fetch stage?
When there is a Jump, or Branch call.
Chapter 26:
What factors affect the processor performance in a computer?
The number of cores.
Clock speed.
Amount, and type of cache memory.
Word length.
Address Bus width.
Data Bus Width
Chapter 26:
What effect does the number of cores have on the performance of a computer?
Process multiple instructions at once.
double cores != double speed.
Chapter 26:
What is Cache?
Small, expensive memory very close to, or inside of the CPU.
Chapter 26:
What are the different levels of Cache?
Level 1 - Extremely fast; individual for cores; usually between 2 KB and 64 KB.
Level 2 - Very fast; shared by cores, but inside CPU; usually between 256 KB and 2 MB.
Level 3 - fast; shared by cores, but outside CPU; usually between 4 MB and 50 MB.
Chapter 26:
What effect does the clock speed have on the performance of a computer?
Clock speed is to do with how fast instructions are executed; high clock speed = better performance.
Chapter 26:
What effect does word length have on the performance of a computer?
Word size is the number of bits that the CPU can process simultaneously.
Typically, word length are 32-bit, or 64-bit.
Chapter 26:
What effect does the Address Buss Width have on the performance of a computer?
Address Bus Width of n can index 2^n different memory locations.
Larger Bus Width = Larger amount of memory locations that can be indexed in one signal.
Instructions can be sent over 2 signals, but this slows down the performance, as every instruction is taking more than twice as long.
Chapter 26:
What is an interupt?
A signal sent by a software program or Hardware device to the CPU.
Interrupts happen when an application program terminates or requests certain services from the operating system.
Chapter 26:
What does the CPU do when it receives an interrupt?
Suspends execution of the running program or process and puts the values of each register and the program counter onto the system stack.
An Interrupt Service Routine is called to deal with the interrupt before the values are retrieved from the system stack, and the Fetch-Decode-Execute Cycle can continue.
Chapter 27:
The Processor Instruction Set refers to 7 types of instruction. List them.
Data Transfer (LOAD, STORE)
Arithmetic Operations (ADD, SUBTRACT)
Comparison Operators (to compare two values)
Logical Operators (AND, OR, NOT, XOR)
Branching (conditional or unconditional)
Logical (shifting)
Halt
Chapter 27:
What are Opcodes made of?
Operation Codes are made of:
Basic Machine Operation
Addressing Mode
Chapter 27:
What are the three main addressing modes?
Immediate
Direct
Indirect
Chapter 27:
What does Immediate Addressing mean for an instruction?
The operand is the actual value to be used.
Chapter 27:
What does Direct Addressing mean for an instruction?
The operand is the memory location of the value to be used.
Chapter 27:
What does Indirect Addressing mean for an instruction?
The Address of the value to use is stored in the operand.
(Go to the location of the operand, then take that value as a new location, use the new location to find the value to use).
Chapter 28:
In Assembly Language, how do you denote values and direct locations?
n = value
Rn = direct location (Register n)
Chapter 28:
What Bitwise Operator is used when converting a binary number to 2’s complement?
NOT
NOT A, +1
Chapter 28:
What Bitwise Operator is used when setting certain bits to 1, but keeping the rest the same?
OR
OR #, 1s in BinaryNum are bits in the original to set to 1
Chapter 28:
What Bitwise Operator is used when masking certain bits from a binary number?
AND
AND #, 0s in BinaryNum are bits in the original to set to 0
Chapter 28:
What happens to the least significant bit in a Logical Shift Right?
How can this be useful?
Shifted into the carry bit space.
So that the least significant bit can be taken to the Status Register independent of the other bits.
Chapter 28:
What is the difference between MOV and LDR in Assembly Language?
LDR loads data (usually) from the RAM into the CPU.
MOV copies data already in a CPU register, into another one.
Chapter 28: There are 18 Assembly Language commands: - 3 Main - 2 Arithmetic - 6 Conditional - 6 Logical - 1 Other
What are they?
LDR - Load memory address to register
MOV - Make a copy of one register to another
STR - Store to memory
ADD - Add
SUB - Subtract
CMP - Compare B - Branch BEQ - Branch if Equal to BNE - Branch if Not Equal to BGT - Branch if Greater Than BLT - Branch if Less Than
AND - Bitwise AND ORR - Bitwise OR EOR - Bitwise XOR MVN - Bitwise NOT LSL - Logical Shift Left LSR - Logical Shift Right
Halt - Stop the program
Chapter 29:
What are the different types of Barcode?
1D - Linear
2D - Quick Response code (QR)
Chapter 29:
What are the four different types of Barcode reader?
Pen-Type readers.
Laser Scanners.
CCD Readers.
Camera-Based Readers.
Chapter 29:
How does a Pen-Type Barcode Reader work?
A Light Source and a Photo Diode are placed next to each other at the tip of a pen.
The tip of the pen is to be dragged across the bars at even speed.
The Photo Diode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the bars and the spaces in the Barcode.
The dark bars absorb light, and the white spaces reflect light, so that the voltage waveform is different in bars and spaces.
With an ADC, this can be converted into a digital representation of the Barcode.
Chapter 29:
What is a benefit of a Pen-Type Barcode Reader?
They are durable, and can be sealed against dirt and dust.
Chapter 29:
What is a drawback of a Pen-Type Barcode Reader?
They need to come into direct contact with a barcode to read it.
Chapter 29:
How does a Laser Scanner work?
In a similar way to Pen-Type Scanners, but they use a laser beam as the light source.
The laser reflects off a moving mirror, which allows the barcode to be read in different positions.
Chapter 29:
What is the most common example of a Laser Scanner?
Supermarket self-scan.
Chapter 29:
What is a CCD Reader?
How does it work?
Charged-Coupled Device Reader.
Uses an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each measures the intensity of the light directly in front of it.
A voltage pattern representing the barcode is generated, by measuring the voltages across each sensor in the row.
Chapter 29:
What is a Camera-Based Reader?
Camera-Based imaging scanners use a camera and image processing techniques to decode a 1D or 2D barcode.
Chapter 29:
What are some benefits to using a Camera-Based Reader?
They can read barcodes off of any surface, printed or onscreen. They can also read damaged, or poorly printed barcodes.
Chapter 29:
What are some examples of where Camera-Based Readers are used?
Age Verification - Scanning driving licence.
Couponing - Discount barcodes can be sent and saved to customers.
Event Ticketing - Confirm purchase at an event.
Consumer Scan - Consumers can scan barcodes to be directed to websites.
Chapter 29:
What is CMOS?
Complementary Metal Oxide Semiconductor.
Similar to a CCD. (Same purpose)
Physically scans for patterns, and stores the input.
Chapter 29:
How does a Digital Camera work?
Using either a CCD or CMOS, images are stored in binary, and can be outputted to a screen.
Chapter 29:
How does a Digital Camera use Colour?
Using a Bayer Colour Filter.
A Bayer Colour Filter is a grid of half green, quarter red, and quarter blue. Using the idea that colours are wave frequencies, only frequencies of a the given colours can pass through the filter.
Every Pixel is made of a 2x2 Bayer Grid: 2 green, 1 red, and 1 blue lights. The colour frequencies are stored separately, but in the same place, so that the pixels can be displayed in a good representation of the original image.
Chapter 29:
What is a benefit to using CCD in Digital Cameras?
What is a benefit to using CMOS in Digital Cameras?
Charge-Coupled Device Readers return a higher quality image.
Complementary Metal Oxide Semiconductors use about 100 times less power.
Chapter 29:
What is RFID?
Radio Frequency Identification.
Consist of a Microchip (~1 mm) and an Antenna (a bit bigger).
Used in tracking. Devices can send signals to the RFID chip and the RFID chip can send signals back.
Chapter 29:
What is the approximate range of an RFID?
300 meters.
Chapter 29:
What is the difference between Passive Tags and Active Tags?
Active Tags are larger because they use a battery to transmit a signal for readers to pick up.
Chapter 29:
When are Active Tags used?
Give an example.
When things are to be scanned from further away.
For example Cars in a motorway toll booth.
Chapter 29:
When are Passive Tags used?
When things scanned are closer, or need to be mass produced.
Passive Tags are cheaper.
For example contactless bank cards.
Chapter 29:
What are the five main components in a Laser Printer?
Control Unit Laser Unit Photosensitive Drum Toner Roller Fuser Rollers
Chapter 29:
What is the role of the Photosensitive Drum in a Laser Printer?
At the start of the printing process, the Photosensitive Drum is negatively charged.
When light hits the Photosensitive Drum, the areas hit by the light become discharged.
The Drum will rotate during the printing process.
Chapter 29:
What is the role of the Control Unit in a Laser Printer?
The Control Unit of the printer is where the image input is received. The Control Unit will break down the image into many tiny grid cells. This grid will then be passed to the Laser Unit.
Chapter 29:
What is the role of the Laser Unit in a Laser Printer?
The Laser Unit receives an input from the Control Unit of the image to be drawn.
The Laser will precisely hit areas on the Photosensitive Drum that represent the grid. This will discharge these areas.
Most Lasers use a polygon mirror so that the laser itself doesn’t have to move.
Chapter 29:
What is the role of the Toner Roller in a Laser Printer?
Toner is a powdery substance. In a Laser Printer, the Toner is negatively charged.
After the Laser Unit has left discharged spaces on the Photosensitive Drum, the Toner Roller presses Toner onto the Drum.
As the Toner is negatively charged, it is repulsed by the negatively charged areas on the Drum, which pushes the Toner into the discharged spaces.
Chapter 29:
What happens just before the Fuser Roller is used in a Laser Printer?
Just after the Toner Roller has applied Toner to the Photosensitive Drum, paper is rolled up from the Paper Tray, under the Drum, where the Toner is pressed onto the paper.
Chapter 29:
What is the role of the Fuser Roller in a Laser Printer?
After the Toner from the Photosensitive Drum has been passed onto the paper, the paper is fed through the Fuser Roller.
The Fuser Roller melts the Toner into the paper, at a high temperature. This is why paper is often still hot when it comes out of the printer.
The paper is then rolled out of the printer.
Chapter 29:
How do coloured Laser Printers work different from black and white Laser Printers?
All printed colours are all combinations of the four: Cyan, Magenta, Yellow, and Black (CMYK).
With coloured printing, the process for a black layer of Toner is repeated 3 more times; for the other colours.
Chapter 29:
*What is the standard DPI of a Laser Printer?
1200 Dots Per Inch.
Chapter 29:
Laser Printers are one type of printer.
What is the other main type?
Inkjet Printers.
Chapter 29:
- What is an advantage of:
- Laser Printers?
- Inkjet Printers?
Laser Printers print much faster:
just under 100 pages per minute, compared to inkjet speeds of 20 pages per minute.
Inkjet Printers can print much higher quality:
Laser printers have a Dots Per Inch (DPI) of about 1200 dots, compared to Inkjet printers with about 600 DPI. It would make sense that Laser printers, with about double the DPI would produce higher quality images, but the ink in Inkjet Printers blend to create higher quality images, where as laser printers are just dots.
Chapter 30:
What are the drawbacks to Secondary Storage, compared to RAM?
Random Access Memory is directly connected to the CPU. Secondary Storage is not, which makes it slower to access data.
Chapter 30:
Why do we use Secondary Storage in Computer Systems?
Secondary Storage is non-volatile.
This means that data is retained when the computer’s off.
Chapter 30:
How do Hard Disks store data?
Ferrous (Iron) particles on the disk are polarised to become either a north or south state: representing 1s and 0s.
Chapter 30:
How do Hard Disk Drives access data?
HDDs have a Read/Write Head (looks like a record player needle) That moves across a part of the disk. Where the disk is spinning (~10,000 RPM), the RW head can reach every part of the disk.
The head can use magnets to create a copy of the polarisation patterns (Read), or polarise locations (Write).
Chapter 30:
What is the Read/Write Head of a HDD attached to?
The Actuator Arm.
Chapter 30:
What are the 3 types of Optical disk?
Give an example for each.
Read Only (CD-ROM) (DVD-ROM)
Recordable (CD-R) (DVD-ROM)
Rewritable (CD-RW) (DVD-ROM)
Chapter 30:
How do Optical Disks write data?
A high-powered laser is used to “burn” (change the chemical properties of) sections of the disk’s surface.
Chapter 30:
How do Optical Disks read data?
A low-powered laser is pointed at the disk. It will reflect into a different place depending on whether or not the spot has been “burned”.
A sensor will measure the light intensity that is reflected back, to determine whether the value is 1 or 0.
Chapter 30:
What are the names of the “burned” bit on an Optical Disk?
What are the other areas called?
Pits (burned)
Lands (not burned)
Chapter 30:
How many tracks does an Optical Disk have?
1
Arranged in a tight spiral.
Chapter 30:
*What are the average capacities of CD-ROM and Blu-Ray?
Why the difference?
CD-ROM 650MB
Blu-Ray 50GB
Although they are the same physical size, the lasers used to burn data into Blu-Rays are much smaller, and more precise. This means that the track can be more tightly wound.
Chapter 30:
How do Rewritable Optical Disks work?
CD-RW uses magnets to change state
DVD-RW can change between Amorphous and Crystalline states, depending on the power of the laser beam.
Chapter 30:
What do Crystalline and Amorphous mean?
Crystalline ordered and tightly packed (like diagram for solids in chemistry)
Amorphous ordered close together, but not as tight and not in as constant of an order (almost diagram for liquid in chemistry)
Chapter 30:
What are the benefits to Optical Storage?
Cheap.
Easy to produce.
Easy to send through post for distribution.
Useful for storing backups.
Chapter 30:
What are the drawbacks to Optical Storage?
Data can be easily corrupted or damaged by excessive sunlight or scratches.
Chapter 30:
What logic are Solid State Drives comprised of?
NAND.
Chapter 30:
What is inside a Solid State Drive?
An array of chips arranged on a board.
Chapter 30:
*What are the different Cell Types of an SSD?
SLC - Single Level Cell (1 bit per cell)
MLC - Multi Level Cell (Multiple bits per cell)
TLC - Triple Level Cell (Specifically 3 bits per cell)
Chapter 30:
How is current stored in SSD cells?
Every cell (every bit) has a pipe-like structure that holds varying amounts of electrons.
Depending on the amount of levels for the cells (SLC/MLC…), the pipe-like structure will be split into this amount of groups. Each group will represent a different range of fullness of the pipe-like structure.
[ The amount of electrons in each cell is rounded to fixed values. ]
Chapter 30:
How do SSDs retrieve values from cells?
Cells are connected to each other Vertically (Hence: VNAND). Rows (“Pages”) (Horizontally) are activated in sync to copy their values into their Bit Line, where they can be processed.
Chapter 30:
What are some advantages to SSDs?
Fast Reading.
Runs Silently.
Very Low Power Consumption.
More Portable.
Chapter 30:
What are some disadvantages to SSDs?
They Deteriorate (And Have a Short Lifespan). They are much more Expensive. They don't have very high writing speed.
