Computer Organisation And Architecture Flashcards
Main memory
Includes RAM and ROM, is volatile memory that provides fast storage and retrieval of data
Address Bus
Bus that carries identification about where data is being sent
Data bus
Bus that carries the data and instruction to and from every component of the computer system
Control Bus
Bus that carries command and control signals to and from every other component of a computer. Also carries the computer’s clock signal
I/O Controller
Piece of hardware that controls the communication of data between the processor and the external hardware device such as keyboard, mice and monitors
Width of bus
Number of parallel wires in a bus
Bus
Series of parallel wires that connects internal components of a computer system, allowing for signals to be passed
Increasing the width of address bus
Increases the range of adresses it can specify,hence increasing the computer’s amount of addressable memory. (2^n)
Increasing width of data bus
Increases the number of bits that can be transferred at one time
Harvard Architecture
Computer Architecture with physically seperate storage and signal pathways for instructions and data. Extensively used in embedded systems like digital signal processing.
Von Neumann Architecture
(4 Points)
-Traditional computer architecture that forms the basis of most digital computer systems.
-A single control unit manages program control flow following a linear sequence of fetch decode execute.
-Both instructions and data are stored together in the same memory and therefore often performs worse than harvard as the same bsuses have to be shared for fetching both.
-Used in everyday general purpose computer systems like phones
ALU
Arithmetic logic unit is the part of the CPU where data is processed and manipulated. This processing and manipulation normally consists of arithmetic operations or logical comparisons allowing a program to make decisions
Control Unit
Responsible for controlling the various components of the processor
Stored Program Concept
Serially fetching and executing machine code instructions stored in main memory by a processor that perfroms arithmetic and logical operations.
Clock
Frequenzt ar which the internal clock generates pulses, measured in hertz. The generated pulses synchronise related components
General purpose register
Small storage locations used to hold data temporarily. They have high read and write speeds
Program Counter (PC) purpose
Used to hold the memory address of the next instruction to be executed in the fetch execute cycle
Current Instruction Register (CIR) purpose
Holds the instruction that is currently being executed by the processor
Memory Address Register (MAR)
Stores the memory address of a memory location that is to be read fron or written to.
Memory Buffer Register (MBR)
Holds the contents of a memory location that has been read from or data that is to be stored. Also called Memory Data Register
Status Register (SR)
Contains a number of bits, the values of which can chnage to indicate the occurrence of an interrupt
Opcode
It is the portion of a machine instruction which specifies the operation to be performed
Operand
The portion of a machine instruction which specifies the operation to be performed.
Interrupt
A signal generated by a source such as hardware or software that causes a break in the execution of the current routine.
Processor Instruction Set
Group of commands for a CPU in machine language. Each type of process has its own instruction set.
Immediate Addressing
Uses the data in the address field as a constant required by the program and not as an address.
Direct Addressing
The value specified by the operand signifies a memory address.
Mnemonic
In assembly language, a mnemonic is an abbreviation for an operation
Interrupt Service Routine (ISR)
Software routine that hardware invokes in response to an interrupt
Factors affecting processor performance (6)
-Number of Cores
-Cache Memory
-Clock Speed
-Word Length
-Address Bus WIdth
-Data Bus Width
How does the number of cores affect processor performance?
Each core can perform its own fetch-execute cycle independently
How does the cache memory affect processor performance?
Cache is used to store frequently used information and reduces time wasted in fetching the same information from main memory time and time again.
How does the clock speed affect processor performance?
The higher the frequency, the more cycles of the fetch-execute cycle can be completed in the same period of time. However, errors can occur when a computer’s clock speed is increased too far
Barcode
Printed diagram that consist of light and dark portions. They contain information. The pattern of light and dark striped in a barcode corresponds to binary. Barcodes can have error detection and prevention methods such as parity bits and check digits built in.
2D vs 1D barcode
2D barcodes contain more information in the same amount of space as a 1D barcode but require more processing in order for the information to be extracted
Barcode Readers
Consist of a laser light source, a lens, photodiodes and a mirror. The mirrot directs 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 processesd to form a digital signal representing the content of a barcode.
Digital camera
Consists of a lens that focuses light onto a sensor. The path of light between the lens and the sensor is regualted by a shutter.
Sensors
-Complementary Metal Oxide Semiconductor (CMOS)
-Charge Couples Device (CCD)
-Both convertincident light into electrical charge, Charge build up in cells, each of which represents a pixel in the image. Once a photograph has been taken, the charge in each cell is measured and converted to a digital value which is then processed by the camera and stored as a digital image.
Colour cameras
There are multiple cells for each pixel, each of which has a filter that only allows in certain wavelengths of light. This lets the camera build up a seperate image for the intensity of each colour which can then be combined to form a full colour photograph.
Bayer filter
Special colour filter used in digital camaras that has the same number of green filters as red and blue combined. Using a bayer filter produces an image that is a closer approximation of what the human eye sees as its mose senstive to green light.
Laser Printer
Output device that produces images on paper from digital signals. They consist of a laser light source, a mirror, a drum, a toner roller and fusers.
Laser Printer Method
When a document is printed, a bitmap of image built in memory from page description. The drum is negatively charged all over before the laser is directed at its surface by the mirror. Areas on which the laser is incident are discharged, leaving behing an impression of the page in electrical charge on the drum. The toner roller dispenses negatively charged toner (type of plastic powder) onto the drum. As opposite charges attract, toner is attracted to the positively charged portions of the drum. Positively charged transfer roller assists transfer toner from drum to paper. The toner is then applied to the paper by the drum before the paper is heared by fusers, fixing the toner to the paper.
Radio Frequency Identification (RFID)
Method of transferring information wirelessly between a tag and a reader. Used in contactless credit and debit cards. Inside an RFID tag is a chip which contains a small amount of memory. Chip is attached to a coil of wire which acts as an antenna.
Secondary Storage
Non-volatile memory that is not directly accessible by the CPU, as its not accessed through the input/output channel because it is an external device.
Hard Disk Drives
Consits of a number of circular platters which are made from a magnetic material. Above each platter hovers an actuating arm on which is a read/write head. The actuating arm allows the head, which changes the magnetic polarity of parts of the platter, to access all portions of each platter
HDD method
Data is written in concentric tracks, each of whihc is further divided into sectors. The platter rotates thousands of times per minute, allowing for good read and write speeds.
Because of the number of moving parts, they are susceptible to damage from movement. This makes them unsuitable for use in portable devices like phones.
Two ways in which hard disk drices can be kept the same size while increasing their capacity
-Adding more platters
-Decreasing the width of tracks
Solid State drives ( SSD )
Consist of NAND flash memory cells and a controller that manages the structure of data on the drive. Data is stored in SSDs in pages, which are combined to form blocks.
NAND flash memory
Non volatile. The memory cells are formed of floating gate transistors which store information by trapping electrical charge.
Disadvantage of SSD
Not capable of overwriting data instead, an SSD’s controller must completely erase the entorety of a page before writting new information on it.
Advantage of SSD
No moving parts, so are capable of far higher read and write speeds than HDDs and are suitable for use in portable devices like phones and tablets.
