XWN740

X-WindowsConfiguring and Using

X-Windows & Hardware(Chapter 1: Pages 11-19)

Agenda

  X Windows & Computer Hardware:

Why Understand Hardware? Elements of X Windows Display

Pointing Devices Keyboard Monitor / Monitor Connections Graphics Card

Calculating Required Video Memory

X Windows & Hardware

  Why Study Computer Hardware for X?

It is always useful to know specific computer hardware specifications to ensure compatability with an OS.

In previous lesson, we saw some examples of howX-windows can be configured for different purposes such as kiosks, accounting systems, etc. Therefore, it is useful to be exposed to a wide range of hardware elements in order to better accomodate employer / client's needs...

Keep an open mind.. Be creative...

X Windows & Hardware

  Types of Computer HardwareManaged by X Windows Server

Zero or more pointing devices Zero or more keyboards One or more video cards, each connected to

one or more monitors

The entire collection of hardware is called a display

Regardless of number of displays, an X windows server must be run for each display

X Windows & Hardware

Pointing Devices:

Pointing Devices allow user to perform common operations such as selecting, moving, resizing graphical elements.

Types of Pointing Devices:

Mice Trackballs Touch Screens

X Windows & Hardware

Keyboards:

Keyboards (when a key or key combination is pressed or released) sends a scancode corresponding to a button location.

Types of Keyboards:

Speciality (e.g. Gaming Console) Numeric Alphanumeric (Various Models!)

Qwerty Dvorak

X Windows & Hardware

Monitors:

Video monitors work by scanning pixels combining intensity of colours red/green/blue (rgb) left-to-right, top-to-bottom to display contents.

Types of Monitors:

Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma Organic Light-Emitting Diode (OLED) Electronic Paper Video Projectors

X Windows & Hardware

Monitor Connections:

There are many potential connection schemes to connect a video card to a monitor.

Types of Monitor Connection Standards:

Television Video Graphics Array (VGA) Digital Visual Interface (DVI) High Definition Multimedia interface (HDMI) DisplayPort

X Windows & Hardware

Video Cards:

Video cards contain the circuitry thatrenders graphics onto the monitor.

There are four main components in a video card:

Memory Graphics Processing Unit (GPU) Bus Interface Video Controller Signal Encryption

X Windows & Hardware

Video Components Diagram:

X Windows & Hardware

Video Memory An area set aside to keep track of the image on the screen

(the framebuffer) and other video related data (pixmaps, save-unders, images). Video cards have swung back and forth between framebuffer on system memory and completely separate bank of memory.

Graphics Processing Unit (GPU) Performs graphics operations such as block move, line

drawing, area fills, shadowing, and texture mapping independently from the system's CPU.

X Windows & Hardware

Bus Interface Used to connect the host system bus to video memory and

Graphics Processing Unit. Common connection path in order of preference are: PCI Express (PCI-E), AGP, and legacy PCI.

Video Controller Generates the video signal by repeatedly scanning the

framebuffer and converting pixel information into the format required at the video connector (eg. digital,digital-to-analog).

Signal Encryption This optional circuit encrypts the signal for content protection

using HDCP or a competing protocol.

X Windows & Hardware

Video Memory Storage

The screen image can be represented in the framebuffer in one of two ways:

1. RGB (colour intensity) for each pixel can be stored in byte segments (modern video cards store RGB information in 3 bytes or 24 bits). For example, the total possible colour range involving this data representation scheme provides:

224 = 16,777,216 colour combinations

This method is more common on modern PCs

X Windows & Hardware

Video Memory Storage

The screen image can be represented in the framebuffer in one of two ways:

2. A colour code for each pixel can be stored. The video controller would look up the colour code stored in a palette to determine the RGB value. This method benefits lower video memory devices.

This method is rarely used on modern PCs, but is common on smaller devices such as PDAs and cell phones.

X Windows & Hardware

Video Memory & Resolution

Screen resolution relates to the number of pixels that are displayed by width and height.

For example:

640 x 480 pixels800 x 600 pixels1280 x 1024 pixels

The higher the resolution on your monitor will require more video memory.

You can use the calculation on the next slide as a guide to determine the required amount of video memory for different video resolutions.

X Windows & HardwareVideo Memory Calculation

Video memory =WidthInPixels x HeightInPixels x BytesPerPixel

For example:

Resolution: 1280 x 1024 pixelsBytes per Pixel: 3

video memory = 1280 x 1024 x 3 = 3,932,160

= 3.75 MB