Fundamentals of Computer Organisation and Architecture Flashcards
What is a processor?
A device that carries out computation on data by following instructions to produce an output.
What does a processor do?
Handles instructions from the user and from hardware and software.
What is a processor made up of?
A thin piece of silicon with millions of transistors and wires called buses which connect the transistors.
What do transistors do?
Control the flow of electrical pulses.
What does main memory do?
Stores data and instructions to be used by the CPU.
What is RAM?
Random Access Memory
Temporary storage that can be accessed quickly.
What is RAM made up of?
A series of chips on which electronic data is stored which are made up of uniquely addressed cells containing instructions or data.
Is RAM volatile of non-volatile?
Volatile
Meaning all contents are lost when the computer is switched off.
Why does bigger RAM improve PC performance?
When a program is run all/ some is loaded into RAM so more applications that can be loaded at one time.
What is ROM?
Read Only Memory
Permanently stores data or instructions.
Is ROM volatile of non-volatile?
Non-volatile.
What is stored in ROM?
Instructions related to the set up of the computer (stored in BIOS).
How is memory organised in main memory?
In a systematic way where different programs are stored in different parts, allowing the CPU to find the data quicker.
What is a bus?
Microscopic parallel wires that transmit data between internal components.
What makes up the System Bus?
Data Bus
Address Bus
Control Bus
What does the Data Bus do?
Transfers data between the processor ,and memory and I/O controllers.
What does the Address Bus do?
Carries the memory address of the next data item or instruction.
What does the Control Bus do?
Sends control/clock signals to registers and the buses.
Ensures the correct data is travelling to the right place at the right time.
Is the Data Bus uni or bi directional?
Bi-directional.
Is the Address Bus uni or bi directional?
Unidirectional
Is the Control Bus uni or bi directional?
Bi-directional
What is addressable memory?
The concept that data and instructions are stored in memory using discrete addresses.
What is word length?
The number of bits that can be addressed, transferred or manipulated as one unit.
What does increasing the number of wires in a bus do?
The amount of data sent depends on the number of wire, so the greater the width the more data transferred per clock pulse.
What are I/O ports?
Physical connections allowing I/O devices to be plugged in.
What are I/O controllers?
Each I/O device has one and it consists of circuitry that handles the flow of data and translates signals from the device into the format required by the processor.
What is architecture?
The way something is built.
What is the Von Neumann architecture?
A technique for building a processor where data and instructions are stored in the same memory and accessed via one bus.
What is the Harvard architecture?
A technique for building a processor that uses separate buses and memory for data and instructions.
What are the advantages of Harvard architecture?
Faster and more efficient as instructions and data don’t share a bus.
What are the uses of Harvard architecture?
Embedded systems where there is a specific use.
What is Digital Signal Processing (DSP)?
A technique that takes continuous real world data and compresses it to enable faster processing.
What is the stored program concept?
The idea that instructions and data are stored together in memory.
What is the Control Unit?
A part of the processor that manages the execution of instructions, ensuring all data is routed correctly.
What is the ALU?
Arithmetic Logic Unit
It processes and manipulates data.
What does the ALU do?
Carries out arithmetic and logic functions.
Compares two values.
What is a clock?
A device that generates a signal used to synchronise the components of a computer.
What is the clocks units?
Megahertz (MHz)
Millions of cycles per second.
What is a register?
A small section of temporary storage apart of the processor.
What do registers store?
Data or control instructions during the FDE cycle.
What does the Status Register do?
Keeps track of the status of various parts of the computer. (overflow error, last calculation, etc.)
What is the Interrupt Register?
A type of Status Register that stores details of incoming interrupts.
What does the Current Instruction Register (CIR) do?
Stores the instructions that the processor is currently decoding/ executing.
What does the Program Counter (PC) do?
Stores the address of the next instruction to be taken from main memory into the processor.
What does the Memory Buffer Register (MBR/ MDR) do?
Holds the data that has just been read from or written to main memory.
What does the Memory Address Register do?
Stores the memory location where data in the MBR is written to or read from.
What is the Fetch part of the FDE cycle?
1) PC holds the address of the next instruction.
2) MAR holds the address of the data to be accessed.
3) Processor sends the address to main memory via the Address Bus.
4) Data is loaded into the MBR by the Data bus.
5) The contents of that memory address is sent to the CIR via the Data Bus.
5) PC incremented.
What is the Decode part of the FDE cycle?
The processor takes the instruction from the CIR and decodes it by referring to the instruction set (either reduced or complex).
What is the Execute part of the FDE cycle?
1) Processor carries out the instruction.
2) Processor fetched the next instruction.
3) Result of the calculations written to a register or memory location.
How can you improve PC performance? (5)
Increase clock speed
Increase bus width
Increase word length
Use multiple cores
Increase cache memory
Why does increasing clock speed improve PC performance?
The clock speed refers to the frequency at which a CPU executes instructions so the CPU can complete more cycles per second, allowing it to perform more tasks in a given amount of time.
Why does increasing bus width improve PC performance?
The width of the bus determines how many bits are transferred in one pulse of the clock so more data can be passed down therefore more data processed in a given time.
Why does increasing word length improve PC performance?
A word is a collection of bits addressed and manipulated as a single unit therefor the amount of data handled per clock pulse increases.
Why does multiple cores improve PC performance?
By allowing the CPU to handle more tasks simultaneously, making the system more efficient.
Why does increasing cache memory improve PC performance?
A cache is where instruction/ data that is frequently needed is stored and cache can be accessed quicker than main memory so programs run faster.
What is an interrupt?
A signal sent by a device or program to the processor requesting its attention.
What are examples of interrupts?
Request for data
User pressing a key
Errors
How are interrupts handled?
1) After each FDE cycle the processor checks the contents of the interrupt register.
2) If an interrupt occurs the processor stops to service it.
3) Pauses the current task by placing the contents of the registers into a system stack.
4) Uses the Interrupt Service Routine which calls the routine required to handle the specific interrupt.
How does the processor prioritise interrupts?
If an interrupt is stopped by another interrupt the processor will asses the priority of the interrupt and decide what needs to be serviced first.
Give 4 examples of the order of priority for interrupts.
Hardware failure
Reset
Program error
I/O
What is an interrupt vector?
Each interrupt has its associated interrupt vector which specifies the address of the routine to handle the specific interrupt.
What is the processors instruction set?
The pattern of 1’s and 0’s which a particular processor recognises as commands and their associated meanings.
What is an opcode?
The commands used in assembly language.
What is an operand?
The value or memory address in assembly language.
What is direct address?
When the operand is the memory address or register number.
What is immediate address?
When the operand is the datum.
What are data transfer operations?
Operations that move data around between registers and memory.
MOV, STR, LDR
What are arithmetic operations?
Operations that perform basic math.
Shift instructions, ADD, SUB.
What are logical operations?
Operations that move the bits around within the operand.
AND, OR, NOT, XOR
What are branch operations?
Operations that allow you to move from one part of the program to another.
BNE, BEQ, BGT, BLT.
How does a digital camera work?
1) The shutter opens and lets light in through the lens.
2) Analogue light waves are focused onto a sensor (CCD or CMOS).
3) As the light hits, its converted into electrons and the amount of charge is recorded for each pixel digitally.
4) Sensor have millions of transistors which stores data for the pixels.
5) The camera will have 3 different RGB filters or sensors.
6) The data is stored on removable storage devices.
7) Data is stored on compressed files.
What are RAW files?
Uncompressed files of the image.
How do barcode readers work?
1) A LED or laser light is passed over an image.
2) A light sensor (photodiode or CCD) measure the intensity of light being reflected back which is converted into a current, generating a waveform.
3) White areas reflect the most and black the least therefore the waveform is used to distinguish the black and white bars.
4) The waveform is converted to digital form using a ADC.
5) Encoding converts it into binary codes.
6) The signal is decoded into a form decodable by software.
What are the different kinds of barcodes?
Universal Product Code (UPC)
QR code
How does a UPC barcode work?
Uses lines of different widths to represent values and has numbers as a manual-override with a check digit.
Why are QR codes better?
They contain a wider range of information.
How do RFID’s work?
1) The tag contains a chip which contains data about the item and a modem to modulate/ demodulate the radio signals.
2) Contains an antennae to send and receive radio signals.
3) Tag could be active meaning it has its own power source (battery).
4) Tag could be passive so it will pick up electromagnetic power when in range of an RFID reader.
5) Signals and therefore data can be transmitted in both directions using radio frequencies.
6) May be used to track the location or the item may transmit data back.
What is a RFID?
A microscopic wireless tracking device.
What are uses of RFID’s?
Tracking individuals
Electronic passports
High value items.
How does a laser printer work?
1) Rotating drum inside the printer is coated in a chemical which holds an electrical charge.
2) Laser beam is reflected onto the drum, where the light hits the charge is discharges, creating an image on the drum.
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 by charging the paper with the opposite charge the toner is attracted to the paper
5) Paper is heat treated to fuse the toner onto the paper.
How does colour laser printing work?
The process is repeated for cyan, magenta, yellow and black.
What are the advantages of a laser printer?
Much faster.
How do Hard Disk’s work?
Made up of multiple disks arranged in a stack with each disk coated in a thin film of magnetic material.
Each disk is metallic and sealed to prevent corruption by debris.
The disks spin and a series of heads read from and write to the disks.
Changes in the direction of magnetism represent 1’s and 0’s.
How are the disks in a Hard Disk organised?
The surface of the disks is divided into circular tracks, with each track further divided into sectors. Each sector can be addressed individually by the operating system.
How do Read-Only Optical Disks work?
Made up of a single spiral track, coated in a protective layer to prevent corruption. A laser will read data by reading the pits and lands in combination with a sensor that measure the amount of light reflected.
The different electrical signals are converted into binary code.
How do writable Optical Disks work?
The disk is coated in photosensitive dye which is translucent. When writing the laser alters the state of the dye spot making it opaque.
The dye reflects a certain amount of light and a read laser interprets the different densities to create binary patterns.
How does a Solid State Drive (SSD) work?
Uses memory cards made up of semi-conductors, which use programmable ROM chips which are stored inside a unit which uses NAND memory, which organises data into blocks with a controller being used to manage the blocks of data.
Data accessed in blocks with blocks allocated to particular semi-conductors.
Why can SSD’s store data without power?
Due to a floating gate transistor in semiconductors, which contains a floating gate and control gate. A thin layer of oxide is placed between the two gates trapping the charge inside the floating gate.
What are the advantages of Hard Disks?
High capacity
What are the disadvantages of Hard Disks?
High power consumption
High latency
Large size
Unrealiable
What are the advantages of Solid State Disks?
Low power consumption
High access speed
Low latency
Reliable
Small size
What are the disadvantages of Solid State Disks?
Expensive
What are the advantages of Optical Disks?
Cheap
What are the disadvantages of Optical Disks?
Low capacity
High power consumption
High latency
Slow access speed
Unreliable
Large size
When are SSD’s used?
In laptops.
When are HDD’s used?
When a large storage capacity is needed (businesses).
When are Optical disks used?
For cheap back-ups.
