Topic 6 - Resource Management

Primary Memory (RAM)

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* What it does:
* Place where all the data / programs currently being processed are kept. 
* Common capacities
* Gigabytes (GB): 1,2,4,8,16 
* Effect on system if too limited
* If there is too little memory the system will need secondary storage, which is a lot slower, through virtual memory. 
* If virtual memory cannot be made or is insufficient the program or data will just not be loaded. 
* It influences how many processes can be done simultaneously.

Secondary Storage (HDD / SDD / Optical drives)

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* What it does
* Place where data / programs can be stored if power is lost (RAM is too volatile)
* Common capacities
* HDD: 500GB, 1TB, 2TB (terabytes)
* SDD: 256 GB, 512 GB
* Optical: CD 650 MB (megabyte), DVD 4.7 GB
* Effect on system if too limited
* No place to “save” work so data can be lost.
* Can also prevent the OS from using storage as virtual memory if RAM fills up. 
* Limits how much data can be kept.

Processor Speed

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* What it does
* A processor (like CPU and others) does all the calculations for a computer system
* Speed is a measurement of how many calculations can be done per second (1 (gigahertz) Ghz = 1 billion calculations per second). 
* Common capacities
* Ghz: 1, 1.2, 2, 2.4, 3.2
* Effect on system if too limited
* Processor will take long to perform tasks

Processor Cores

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* Processor cores
* What it does
* Each processor has at least 1 ALU or core. If you have two you can do two operations at once. 
* Common capacities
* 2 core = dual core, 4 = quad core, 8 = octa, etc
* Effect on system if too limited
* If you only have one you can only perform one set of operations or calculations at a time. If you have two or more you can do more calculations in the same time frame. 
* It affects how many tasks a system can cope with simultaneously.

Bandwidth (network transmissions)

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* What it does
* Measurement of how much data can be sent at the same time in a certain time frame. 
* Common capacities
* Measured in bits per second (bps)
* Broadband (high speed internet connection) =  16-100 Mbps. 
* LAN = up to 1 Gbps
* Effect on system if too limited
* Limiting bandwidth means data will take longer to move between two points. 
* Affects how long it takes before data can be processed in its entirety.

Screen Resolution

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* What it is
* Measurement of the number of pixels in height times width of display
* Effect on system if too limited
* The number of pixels that can be displayed is less, so the display may be blocky / pixelated. 
* Lower resolutions  = smaller file size but poorer quality images. 

Sound Processor

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* What it does
* Sound reproduction is done by a separate processor freeing up CPU for other calculations. 
* ALso contains a bank of ‘sampled’ sounds to reproduce better quality music / audio. 
* Common seen in
* Home theater systems
* Movie theaters
* Effect on system if too limited
* CPU is taxed with having to process sound and it slows down the system overall. 
* Overall quality is not as high in a system with a sound processor. 

Graphics Processor (GPU)

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* What it does
* Complex graphic processing (like rendering 3D)
* Common seen as
* Nvidia or ATI graphics cards
* Effect on system if too limited
* If CPU has to do graphics processing it will take longer or be limited.

Cache

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* What it does
* Contains the instruction / data the CPU is likely to request next from RAM. It massively speeds up processing as the CPU does not have to ‘wait’ for instructions to arrive from RAM.
* Common capacities
* MB: 1 to 128
* Effect on system if too limited
* CPU will have to ‘wait’ for instructions / data to be fetched from RAM - slowing down the system. Users experience a ‘sluggish’ system.

Network Connectivity

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* What it is
* Each networked card connects to a particular type of network media (cable / wireless signal)
* Commonly found as
* Network interface card (NIC) = LAN / ethernet cables
* Wireless network interface controller (WNIC) = wifi signals
* Bluetooth = bluetooth signals
* 3G radio = cellular signals
* Effect on system if too limited
* Limited connection types limits the way data can be sent or received in a system
* Speed can also be a factor

Resources in the Mainframe

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* Processor
* Thousands of cores
* Primary memory
* Vast amounts
* Secondary memory
* Vast amounts
* Common use
* Used in large companies
* Used for weather/financial models and predictions
* Used to ‘virtualize’ smaller computers
* Mostly CRAY or IBM

Resources in Servers

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* Processor
* Many high spec PCs running in parallel (3-4 GHz)
* Primary memory
* Big capacity (32 GB+ per machine)
* Secondary memory
* Terabyte per machine
* Common use
* To serve networks
* Data centers for cloud storage
* Size varies according to use

Resources in PCs

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* Processor
* Single processor (multiple cores) 1-4 GHz
* Primary memory
* 2-16 GB
* Secondary memory
* 256 GB to 2 TB
* Common use
* Companies and schools where portability is not needed
* Can be expanded by adding expansion or graphics cards
* Used to be the most common type of personal computer - not anymore.

Resources in Cell Phones

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* Processor
* Single / multicore
* Primary memory
* 1 - 3 GB
* Secondary memory
* Usually limited but can be upgraded (MicroSD card)
* Common use
* Most common personal computing deceive in the world
* Getting more capable of rivaling PCs/laptops
* Biggest constraint is screen size and input options (lack of a physical keyboard)

Resources in Tablets

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* Processor
* Single / multicore
* Primary memory
* 1 - 4 GB
* Secondary memory
* Usually limited but can be upgraded (MicroSD card)
* Common use
* Very common for media consumption
* Getting more capable of rivaling PCs/laptops
* Biggest constraint is lack of physical keyboard

Resources in Digital Cameras

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* Processor
* Single core
* Primary memory
* Limited
* Secondary memory
* Expandable through the use of memory cards (SD / compact flash / memory stick)
* Common use
* For higher end photography
* Most digital cameras now integrated in mobile phones / laptops / tablets

Limitations in 3D graphics rendering

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* Single processor computers may not be able to render 3D graphics as effectively as multicore systems with a GPU. 

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* Primary memory
* The game may not load, or it could fall back on secondary storage. This will cause the entire computer to significantly slow down. 
* Secondary storage
* Limits how much data can be kept by the game. Also may cause your progressive to not save. 
* CPU speed
* The CPU will take even longer to perform, making it take a long time to render the graphics. 
* CPU cores
* The system will not be able to cope with all the graphics programming and movements at once. Less cores means that less things can be done at once. Will severely slow down play time.
* Connectivity
* Slows it down and limits what type of games and data can be played / sent. 

Problems from Limiting Resources in a Computer System

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* User time wasted if primary memory is too small or processor speed inadequate. 
* Multi-access and multi-programming environments should be considered as well as single-user systems. 
* Multi-user system
* Either many users on the same machine
* Or many users connected to the same network
* Multiprogramming system
* Multiprogramming system = systems that can have different programs or apps installed. 
* Phones and laptops
* Switch
* Single programming system = can only run one program / set of programs
* A kindle 

Scheduling

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* Scheduling is the method by which work is assigned to resources that complete the work. 
* The work could be processes which are in turn scheduled onto hardware resources such as processors, network links, or expansion cards. 
* The algorithm used could be as simple as a round-robin in which each process is given equal time in a cycling list. So process A executes for 1ms, then process b, then c, then back to A.

Policies

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* The policies **what** is to be done while the *mechanism* specifies **how** it is to be done. 
* For instance, the timer construct (limiting the time a process can use the CPU for) thereby ensuring CPU protection is a mechanism. 
* On the other hand, the decision of how long the timer is set for a particular user is a policy decision. 
* The separation of mechanism and policy is important for flexibility to a system.

Multitasking

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* Multitasking, in an operating system, is allowing a user to perform more than one computer task (such as the operation of an application program) at a time. 
* The operating system is able to keep track of where you are in these tasks and go from one to the other without losing information. 
* Almost all of today’s operating systems can do this. 
* When you open your web browser and then open Word at the same time, you are causing the operating system to do multitasking.

Virtual Memory

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* Virtual memory is a feature of an OS that allows a computer to compensate for shortages of physical memory by temporarily transferring pages of data from RAM to disk storage. 
* Eventually, the OS will need to retrieve the data that was moved temporarily to disk storage - but remember, the only reason the OS moved pages of data from RAM to disk storage was because it was running out of RAM.

Paging

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* When using virtual memory, the OS needs to retrieve the data that was moved to temporary disk storage. This is a problem as there is no memory left to have the pages be brought back. 
* To solve the problem the operating system needs to move other pages to the hard disk so it has room to bring back the pages it needs. 
* This is a pagefile or swap file
* It is carried out by the computer’s memory manager unit. MMU.

Memory Management Unit Algorithms

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* Least Recently Used LRU
* Least Frequently Used LFU
* Most Recently Used MRU

Interrupt

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* An interrupt is a signal to the processor emitted by hardware or software indicating an event that needs attention. 
* An interrupt alerts the OS to a high-priority condition that needs to interrupt the current code. 
* OS responds by suspending current activities, saving its state, and executing a function called interrupt handler. 
* After the handler finishes normal activities are resumed. 
* Two types of interrupts
* Hardware interrupts
* Software interrupts

Polling

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* The process where the computer or controlling device waits for an external device to check for its readiness or state, often with low-level hardware
* A printer is connected via a parallel port, the computer waits until the printer has received the next character
* It is usually more efficient to use interrupts because it can reduce processor usage and bandwidth consumption.

Advantages of a dedicated operating system

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* Security: a dedicated operating system ensures a higher level of security.
* Customizability: when custom made to do a specific function it works at maximum efficiency
* Modify priorities: can make running some devices easier to use or better suited to the audience. You can eliminate certain aspects of the os which are not needed, reducing size of the os, therefore reducing the amount of secondary memory and RAM being used.

Abstraction leading to simplicity

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* Users and applications do not see the hardware directly, but view it through the OS.
* This is used to hide certain hardware details from users and applications (abstraction)
* Users cannot see changes in the hardware. It can be used to make related devices appear the same from the user’s point of view. 
* IE hard disks, floppy disks, USB keys.

Drive Letters

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* A drive letter is a single alphabetic character A through Z that has been assigned to a physical drive or drive partition in the computer. 
* A computer with a floppy drive has a drive letter of A assigned to the drive. 
* All computers with a hard drive will always have the default hard drive assigned to a C drive letter. 
* CD-ROM or other drive is the next drive letter (eg D), etc.

JVM

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* A java virtual machine - JVM interprets compiled Java binary code (called bytecode) for a computer’s processor (or hardware platform) so that it can perform a java program’s instructions. 
* Each platform gets its own JVM so that Java code can run on any platform.

Operating System role

* Device Configuration
* file management
* memory management
* interface platform
* managing primary memory
* virtual memory
* secondary storage
* providing an interface
* time-slicing
* interrupt handling

Device configuration

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* controls peripheral devices connected to the computer
* Use of drivers (specially written, individualized) translation programs, the other programs can use and control peripheral devices (like keyboards, mouses, printers, etc).

File management

transfers files between main memory and secondary storage, manages file folders, allocates the secondary storage space, and provides file protection and recovery

Memory management

allocates the use of RAM (random access memory) to requesting processes

Interface platform

allows the computer to run other applications

Manages primary memory

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* The OS has to ensure that each process (program) runs in its own allocated memory space
* If programs interfere with each other’s memory space it could cause many problems and security issues

Virtual memory

A feature of an OS that allows a computer to compensate for shortages of physically memory by temporarily transferring pages of data from RAM to disk storage.

Manages secondary storage

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* Manages by providing structure and access methods to these structures
* The folder-structure or the directory-structure
* Also manages the security access of these folders

Provides an interface

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* User interface is used to interact with the computer to perform various tasks. User gives commands to computer and enters the data into the computer. The operating system then translates the input/output and sends it to the correct memory address/folder access to be processed. 
* There are two types of OSs based on user interface:
* Graphical User Interface Operating System (Windows)
* Command Line Operating System (Linux Terminal)

Time-slicing

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* With a multi-user system, a time-slice is the set amount of processing time each user gets
* With a single-user system, a time-slice is the set amount of processing time each program gets
* Slices are alternately processed to give the illusion of many tasks happening at once.

Interrupt handling

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* An interrupt handler is a function in of the OS or a device driver, whose execution is triggered by the reception of an interrupt. 
* Interrupts are used to handle high-priority conditions that require the interruption of current code the processor is executing
* For example: pressing a key on a keyboard or moving the mouse, triggers interrupts that call interrupt handlers which read the key, or mouse’s position, and copy the associated information into the computer’s memory.