Theory: Computer Architecture Flashcards
What is the role of the processor?
To execute program instructions in order to run applications.
Name two types of main memory
-Random access memory (RAM)
-Read only memory (ROM)
Which is usually faster: main memory or secondary storage?
Main memory
Name two types of information that may be held in main memory
-Program instructions
-Frequently used data
What is meant by a bus?
A series of parrallel wires that connects internal components of a computer
Which bus is used to transport memory addresses?
Address bus
Which bus is used to send information to and from different components?
Data bus
How many parallel wires does the address bus have?
8
An address bus with n parallel wires can allow how many addressable memory locations?
2^n
What effect does increasing the width of the data bus have?
Increases the volume of data that can be transferred at any one time.
What is the role of the control bus?
Carries control signals, including the system clock which regulates the operation of the computer system
What is the name given to hardware that controls the communication of data between the processor and external hardware devices?
I/O controllers
Describe the main difference between Harvard and Von Neumann architecture.
Von Neumann consists of shared memory for instructions and data, Whereas Harvard architecture has them seperate
What is the drawback of Von Neumann architecture?
An instruction fetch and data operation cannot occur at the same time
Is RAM or ROM volatile or non volatile
RAM is volatile
ROM is non volatile
What is meant by the stored program concept?
Machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations
What is an advantage of using the stored program concept?
Allows one computer to run several different programs
When using the stored program concept, what two things could the contents of a memory location be interpreted as?
- Instructions
- Data
Which type of architecture is extensively used in embedded systems?
Harvard architecture
Which type of architecture is used in general purpose computer systems?
von Neumann
Name the two architectures on which stored program computers can be based.
Harvard architecture, von Neumann architecture
Which type of register is the status register: general purpose or special purpose?
Special purpose
Which of the following is not found within the processor? Control unit, Main memory, Buses
Main memory
For what do the letters ALU stand
Arithmetic Logic unit
What effect does increasing the width of the address bus have?
Increases the computers amount of addressable memory
Which register hold the instruction that is currently being executed by the processor?
Current instruction register
What is cache?
A small portion of fast memory used to store frequently used information in the processor
What name is given to small storage locations used to hold data temporarily in the processor?
Registers
What is meant by this assembly language instruction?
STR R3, 33
Store the value in register 3 into memory location 33
Which register holds the contents of the memory location that has been read from or data that is to be stored?
Memory buffer register
Which part of a computer’s processor generates signals at a regular frequency?
Internal clock
Which special purpose register is abbreviated as MAR?
Memory Address Register
What name is given to the data to be used in an instruction: opcode or operand?
Operand
Form an assembly language instruction that would mean: “Add the value in register 4 to the value in register 5 and store the result in register 3”
ADD R3, R4, R5
In which stage of the fetch decode execute cycle is the program counter incremented?
Fetch
Between which two stages of the fetch decode execute cycle is the status register checked?
Execute and fetch
What name is given to the group of instructions that a processor can carry out?
Instruction set
In which addressing mode does the value specified by an operand signify a memory address?
Direct addressing
Name two parts of a barcode reader
Laser, lens, photodiodes, mirror
Which parts of a laser printer heat the paper, fixing the toner to the page?
Fusers
What is a bayer filter?
A bayer filter is a colour filter array (CFA) for arranging RGB color filters on a square grid of photosensors
Where is the Bayer filter used?
used in most single chip (CCD or CMOS) digital image sensors used in digital cameras, camcorders and scanners to create a colour image.
Define CCD and CMOS
Charge coupled device, complementary metal oxide semiconductor. Two different technologies for capturing images digitally
What is the difference between CCD and CMOS ?
CMOS faster than CCD. CCD allows for higher video frame rates. CMOS imagers provide higher dynamic range and require less current and voltage to operate.
Why is a bayer filter used?
allows photosensors, which normally only record light intensity, to record light wavelength as well.
What does a bayer filter look like? Draw it
Which technology is used for transferring information wirelessly between a tag and a reader?
Radio frequency identification (RFID)
What is RFID?
a technology that uses radio waves to passively identify a tagged object
What type of diagrams, consisting of light and dark portions, contains information that can be read by a computer?
Barcodes
What type of diagrams consisting of light and dark portions contain information that can be read by a computer?
Barcodes
Which type of RFID tag can be read from many metres away?
Active
What is the difference between active and passive RFID tags?
Where a passive tag has no internal power source and obtains its operating power from the radio frequency energy transmitted by the RFID reader, active RFID tags come equipped with its own battery and internal transmitter in the form of a beacon or transponder, typically allowing data to be rewritten and modified.
In a hard-disk drive, what is mounted at the end of an actuating arm?
The read/write head
What is an actuating arm?
The access arm is in every mechanical hard drive with a similar to the arm of a record player. As the platter spins, the access arm adjusts along the axis point to move the read/write heads to read/write/delete information
Which form of secondary storage is best suited for use in phones and tablets?
Solid-state drives (SSDs)
Give the three types of secondary storage device with example.
-Magnetic storage devices, hard disk drives
-optical storage devices, CD, DVD, Blu-ray disks
-solid state storage devices, solid state drives and USB memory sticks
Which form of secondary storage typically comes in capacities between 500 GB and 5TB?
Hard disk drives (HDD)
Name one way of increasing the capacity of a hard disk drive without altering its overall size
- Adding more platters
- Decreasing the width of tracks
What are tracks in hdd?
-The data is stored on the disk in thin concentric bands called tracks.
-There can be more than a thousand tracks on a 3 1/2 inch hard disk.
-Tracks are a logical rather than a physical structure
-Are established when the disk is low level formatted
What is a platter in hdd?
One or more aluminium, glass or ceramic disk coated in a magnetic media located within the hard drive
Which part of a digital camera regulates the path of light
Define a bus
A bus is a communication system that transfers data between components inside a computer, or between computers
A set of parallel wires that connect together components in the CPU in order to pass signals between them
What advantages does Harvard architecture have over Von Neumann architecture? What is it used for?
-higher performance, faster
-internal processor structure for caching
Microprocessors, embedded devices/systems, microcontrollers
Stored program concept WHAT IS IT??
-Instructions or programs are stored with data in main memory// RAM
-Program is run by fetching decoding and executing instructions from main memory in sequence.
-Program can be replaced by loading another program into main memory.
-contents of a main memory location can be interpreted as either and instruction or data
Name four system hardware decisions that affect the performance of the processor: plus effects.
-multiple cores
-cache memory
-faster clock speed
-bus speed/size
-heat dissipation
Name an Assembly instruction and what it does:
ADD
SUB
DIV
LSR
LSL
LDR
LDA
BNE
CMO
What is ROM, give an example:
-Read only memory
-can’t be written to
-bootstrap loader, loads bios
Name one of the technological factors to consider when selecting a mainboard:
-number of RAM ports
-CPU compatibility
-I/O
Name two of the three system busses
-address bus
-control bus
-data bus
Give one difference between Harvard and Von Neumann architecture
harvard architecture stores instructions and data seperately whereas von neumann stores instructions and data in the same memory space.
Name two registers
-CIR
-MDR
-MAR
-PC
-ACC
-GPR
What does the program counter do?
Stores the memory address of the next instruction to be executed
What is the difference between direct and immediate addressing modes?
Direct addressing modes contain the memory address of the data being used, whereas immediate addressing modes contain the data being used
-# is used to show immediate
Explain parity checks
Parity checks contain a bit that indicates whether the number of ones is odd or even
BNE, what does it do?
‘Branch not equal’, checks if two values are equal and branches depending on if they are equal or not.
Explain how the width and speed of a data bus can affect performance
What is stored in cache?
Frequently used instructions and data
CMP, what does it do?
Compares two values
Name and explain a factor that can affect CPU performance
-multiple cores
-clock speed
-bus width/speed
-heat dissipation
Explain the three levels of cache and what they are used for
Level 1: smallest, but fastest. Split into instructions and data cache.
Level 2: more spacious than level 1 cache, but slower as it is further away than L1
Level 3: more spacious, again slower. Specific memory dedicated to improving the performance of L1 and L2
Role of ALU
simple arithmetic and logic operations
Role of Control Unit
Controlls the various components of the processor. Controls fetch execute cycle
Role of registers
Small storage locations that hold data temporarily, high read and write speeds
What are general purpose registers?
Used as storage for any data that is required by instructions during execution
What are special purpose registers?
Assigned to the storage of specific information
List the registers:
-program counter
-current instruction register
-memory address register
-memory buffer register
-status register
What does the program counter do?
Holds the memory address of the next instruction
What does current instruction register do?
Holds the instruction currently being executed by the processor
What does the memory address register do?
Stores the memory address of a memory location to be read from or written to
What does the memory buffer register do?
(Also called memory data register) holds the contents of a memory location that has been read from or data that is to be stored.
What does the status register do?
Contains a number of bits which change to indicate an interrupt
What is the system clock used for?
A timing signal that changes at regular frequencies. Synchronises the communication between components of the processor and the rest of the computer system.
What are the four different types of barcode scanner?
-pen style reader
-laser reader
-CCD reader
-camera based readers
What is the disadvantage of CCD sensors in cameras?
-bulkier
-uses up to 100 times more power than CMOS
What is an advantage and disadvantage of CMOS?
-not as bulky
-uses much less power than CCD
-lower quality images
How are coloured pictures captured?
-sensors (like ccd or cmos) are placed behind a colour filter
Describe two methods of coloured image capturing
-incoming light is split into three separate parts and each is passed through a red blue and green filter, higher quality images but bulky
-a mosaic of red, blue and green filters is placed in front of the sensor. Software makes approximations for each pixel based on values of surrounding pixels. Produces approximate, but still accurate inages. More compact.
Describe the parts of a laser printer
-powdered ink (toner) stored in hoppers
-negatively charged drum
-laser
Describe the process of a laser printer
-a bitmap image is generated of the image
-the laser draws a mirrored negative version of the image onto the drum as it turns
-the areas that the laser hits of the negatively charged drum, lose their negative charge
-the drum rotates past the toner hoppers
-charged toner is attracted to non-lasered areas of the drum.
-toner particles are then bound to the paper using heat and pressure as the drum rotates over it.
What is a disadvantage of a laser printer?
-Printed image will not be photorealistic
-the process would need to be repeated 4 times for a colour image, for cyan magenta yellow and black toner.
What is a disadvantage of active RFID tags?
Must be much larger to accommodate for battery
