Michaelmas 2023 Flashcards
Architecture of the CPU CPU Performance Embedded Systems Primary Storage Secondary Storage Networks
What is the CPU responsible for?
Executing the instructions given to it in a program
What is a microprocessor?
An integrated circuit that is made up of millions of transistors
What does the CPU contain?
CU, MAR, MDR, ALU
What is the Von Newmann Architecture?
The way the CPU is designed, and executes the program instructions
What is the Von Newmann Bottleneck?
A limitation on CPU performance caused by the CPU having to wait for data. (Processor speed is very fast, data transfer from RAM is slower)
What is a bus?
A collection of wires that carry signals or connections between the components in the computer system
Control bus
Transfers control signals between the CPU to the memory
Data bus
Transfers data between the CPU and the memory
Address bus
Copies memory address from the CPU to the memory
Fetch, Decode and Execute Cycle
Address of instruction copied from PC to MAR, then copied to MDR by data bus, then copied to CIR. Instruction is decoded by the CU, and is performed
ALU (Arithmetic Logic Unit)
Performs arithmetic and logical operations
CU (Control Unit)
Coordinated actions of the computer, and controls the flow of the data between CPU and i/o devices
Clock
Pulses are sent out by a vibrating quartz crystal to synchronise FDE and operation of the CPU
Overclocking
Adjusting the clock to run faster than the CPU is designed for
Cache
A small amount of energy that is part of the CPU, temporarily holds data and instructions CPU is likely to reuse
More cache
means more data is can be stored closer to the CPU
More cores
(processing units) means more power to run multiple programs at the same time
Decoder
Decodes program instruction from memory and decides what to do with it, then sends control signals to other components to carry them out
Registers
Small high-speed memory locations in a CPU which stores instructions and data that are used in the FDE cycle
-Program Counter (PC)
Holds memory address for the instruction of each cycle, increased each time an instruction is carried out
-MAR (Memory Address Register)
Stores the address of the next item of data that is needed by the processor
-MDR (Memory Data Register)
Stores data from memory until it is used
-Accumulator
Stores results of logical and arithmetic operations
Embedded system
Computer system built within a larger device, and limited to a certain number of tasks at an efficient rate
Characteristics:
- limited number of components
- specific hardware necessary
- clock speed much lower than general purpose computers (100MHz)
Advantages:
- easier to design
- cheaper to produce
- more efficient than PC
Disadvantage:
Narrow functionality
Computer Network
Two or more devices joined together to share data
Node
An entity or addressable device on a network that can be managed
Standalone Device
Computer or device that is not connected to the network
Transmission Media
A method of carrying data signals from one computer to another
Features of LAN
Communications media is owned by LAN, owner is responsible for setting up and maintaining the network
Advantages:
- Users can share resources and files
- Files can be backed up
- Protection from malware can be managed centrally
Disadvantages:
Cost (must buy, install and maintain), malware (bugs and viruses can spread)
WAN
Made of several different LANs connected together, used by companies to connect offices all over the world
Advantages:
- Shares information over a large area
- Supports global market and global businesses
- Centralised It structure
Disadvantages:
- Buying access can be expensive as you pay through broadbands at home
- Relies on internet service providers to fix problems
Bandwidth
How much data can be pushed across a connection in a given amount of time
Error Rate
Number of mistakes that occur during data transmission
Latency
Time between the transmission of data packet and the receipt of a message across a network
Data Collision
Result of simultaneous data packet transmission between two or more network domain devices or nodes (causes transmission errors requiring data to be resent)
Factors that affect network performance:
- Latency
- Number of users
- Bandwidth
Wireless connections have more or less bandwidth than wired?
Less
How do errors occur
By interference from other networks, weak wifi, data collisions
Round-trip Latency
The time computer A has to wait until it receives the acknowledgement for the IP packet for computer B
Client-server Network
Network where a server provides data and services for client computers
Peer-to-peer
Network where computers have equal status, each peer performs tasks for itself whilst other tasks can be shared between the peers in the network (COMPUTERS COMMUNICATE DIRECTLY WITH EACHOTHER WITHOUT A CENTRAL SERVER)
Network Architecture
A set of rules on how computers are organised in a system and how tasks are allocated between these computers
Server
A computer dedicated to providing information in response to requests, classified by the type of service they provide
Clients
Computers which users login to the network
Client-server Advantages:
central management of files and backup procedures, security and software updates, logins and user activity can be monitored
Disadvantages:
Server hardware is expensive and costly to manage, network is reliant on the server, services can be overwhelmed by requests
P2P Advantages:
Easy and cheap to set up, robust
Disadvantages:
File management and backups performed individually, network less secure (one insecure computer can allow malware into the entire network)
Networking Hardware
Hardware needed to set up a network
NIC (Network Interface Card)
Enables a device to connect to a network, each unique MAC address to enable data to be sent to that device on a LAN
Switch
Intelligent device to provide wired connections for nodes on a LAN
Hubs
Broadcasts to all connected nodes, generating a lot of data traffic
Hubs and Switches
Connect wired devices on a LAN
WAP
Device that allows wireless devices to connect to a wired network
WAP Features
Data transmitted to all devices, encryption required, bandwidth less than wired connections
Connects to a router, but can also be an integral part of the router itself
Disadvantage:
Bandwidth is shared with any old user with the password
Router
Networking device which connects different networks
Copper cables types
- Coaxial ( signal degenerates quickly over distance)
- Unshielded twisted pair (twisting reduces signal degeneration)
- Shielded twisted pair (copper shielding reduces interference)
Advantages:
Cheap and more adequate for wiring in a LAN
Disadvantage:
- Lower bandwidth
-can only be used over a short distance - Interference
Fibre-optic
Data transmitted along thin glass cables using light pulses, cables are thin and bundles together to increase bandwidth
Advantage:
- Data can be transmitted at very high speeds, and over long distances without losing signal strength
- Hard for hackers to intercept signals
Disadvantage:
Replacing copper cables with fibreoptic is expensive
Internet
Global communication system including hardware and infrastructure
World Wide Web
Collection of services hosted on the internet
Network Protocol
Standard that specifies format of data as well as the rules to be followed during transmission
Satellite Internet
Constellation of artificial satellites providing internet service
Advantages:
Enables internet access in remote areas, potentially faster than ground-based access
Cloud Computing
Practice of using a network of remote servers hosted on the internet to store, manage and process data, rather than a local server or a personal computer
File servers
Used to store and manage files for network usersS
Advantages of Cloud Computing
- Do not need to buy secondary storage
- Backups done, multiple copies of data in different locations
- Enables multiple users to access and modify files
Disadvantages:
- Pay for internet access
- Could lose password, dependent on Cloud Service Provider
- Target of sophisticated hackers
Environmental Considerations
Enables Work from Home, which reduces pollution and energy consumption
Huge amounts of land are used to build data centres
Network Architecture
Logical structure of the network
Network Topology
Physical layout or configuration of a network
Star Topology
Nodes are connected to a central device which is connected to one or more servers
Advantages:
- easy to add new nodes
- management of network can be done centrally
Disadvantages:
- requires extra hardware (central device is high maintenance)
- reliant of central device
Mesh Topology
Multiple communication pathways between nodes, no central point
Paid for when reliability of network communication is very important (military)
Advantages:
- multiple pathways
- no single device failure compromises network
- fast data transfer
Disadvantages:
- very expensive to connect all nodes
- Adding new node is complex
Partial Mesh Topology
Most nodes are interconnected, but some are connected to only some of the other nodes
Primary Storage
Storage used for data currently in use, eg RAM, ROM, cache, registers, virtual memory
Secondary Storage
non-volatile long term storage, device that provides permanent storage for data
RAM
Random Access Memory, contains millions of memory locations, each with a distinct address
ROM
Read Only Memory, stores basic input/output system and bootstrap program
Bootstrap Program
Initialises all aspects of system, loads operating system into RAM and starts execution
Virtual Memory
Used when physical RAM is full, less used data copied from RAM into virtual memory. When it is needed, it is copied back
Disadvantage:
Data access on hard disk much slower than RAM<, computer performance will be affected
