Pavan Burbure

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Tuning X for the perfect display

• Pavan Burbure
• Distributed under the GNU Free Document License

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Agenda

• The CRT monitor
• The Frequencies
• The Modeline
• Resolutions
• Refresh Rates
• Positioning the display
• Managing display with the other OS
• Non-standard resolutions

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The CRT monitor

• Draws line by line horizontally(HR pixels)
• Draws VR such lines vertically to complete the
  screen
• Draws RR such screens in a second

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The Frequencies

• Refresh rate (RR / VSF / VertRefresh) the
  number of times the screen is drawn in 1s
• Horizontal Sync (HSF / HorizSync) The number of
  lines drawn in 1s HSF RR VR
• Pixel Rate (DCF) The number of pixels drawn in
  1s (Note Less than 80 of these pixels are
  actually visible) DCF HSF HR

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The Modeline

• Modeline 49.5 800 832 912 1056 600 601 604 625
• 49.5 - DCF
• 800 - HR 600 - VR
• 832 - Sync Start 601 - Sync Start
• 912 - Sync End 604 - Sync End
• 1056 - HFL 625 - VFL
• HSF DCF/HFL 49.5M/1056 46.87kHz
• VSF HSF/VFL 46.87k/625 75Hz

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Resolutions

• X chooses the resolution based on HorizSync
  VertRefresh
• Usually chooses the highest resolution
• To choose a specific resolution, specify Modes in
  Screen section

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Refresh Rates

• X chooses the refresh rate based on VertRefresh
• Usually makes a mistake!
• To choose a specific rate, limit VertRefresh or
  specify your own Modeline
• Theoritically just decrease/increase the DCF

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Positioning the display

• Increasing Sync start moves the display left or
  up
• Decreasing Sync start moves the display right or
  down
• Increasing Total makes the display narrower or
  shorter
• Decreasing Total makes the display wider or
  taller
• Use xvidtune to try this on the fly

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Managing display with the other OS

• Run X at the same RR
• Position the display using xvidtune
• Add/Change the Modeline in XF86Config

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Non-standard resolutions

• 832x624, 936x702, 1200x900 possible as long as
  you do not exceed the maximum monitor frequencies
• Sample Modeline"832x624" 57.3 832 864 928 1152
  624 625 628 667

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Disclaimer You may end up with blown Monitors!!
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Thank You

• Contact pavanburbure_at_yahoo.com