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Fixing overscan issues

Overscan is a common issue with HDTVs, but there are some steps you can take to disable overscan:

  • Check the TV’s settings and see if there is a way to disable overscan.
  • If you don’t need HDMI audio, use CRU to delete the extension block, or edit the extension block and delete HDMI support. This will cause the GPU to send a DVI signal, which most TVs will not overscan. This will not work with 4K TVs.
  • Use CRU to edit the affected detailed resolution and choose “LCD reduced” timing. This will use a different timing standard that some TVs will not overscan.
  • Use the graphics driver’s control panel to scale the image down. This will affect image quality.

List of EDID editors

Custom Resolution Utility (CRU) is an EDID editor that focuses on custom resolutions. Besides CRU, here are some other EDID editors:

  • Phoenix EDID Designer – Commonly referenced on forums but out of date. Does not support EDID 1.4 or extension blocks.
  • Deltacast E-EDID Editor – Similar to Phoenix but updated to support EDID 1.4 and CEA-861 extension blocks.
  • AW EDID Editor – Supports EDID 1.4 and CEA-861 extension blocks but not HDMI data blocks. Has a Mac version as well.
  • Advantiv EEditGold and EEditZ – The most complete EDID editors, but I find them to be buggy.

CRU can import and export files compatible with these editors.

Timing parameters explained

Active is the visible resolution.

Blanking is the period between each line (horizontal blanking) and each frame (vertical blanking). This was originally intended to give CRT monitors time to move the electron gun. LCD monitors don’t need as much time, so the blanking can be reduced.

Blanking = front porch + sync width + back porch

Front porch, also known as sync offset, is basically padding before the sync pulse.

Sync width is the duration of the sync pulse. The sync pulse marks the start of the next line (horizontal sync) and the next frame (vertical sync).

Sync polarity is whether the sync pulse voltage goes up (+) or down (−). Most monitors can handle both.

Back porch is basically padding after the sync pulse, before the start of the active pixels.

Total is the total number of pixels including blanking.

Total = active + blanking

Frequencies

Refresh rate is the number of screen refreshes per second.

Horizontal scan rate is the total number of horizontal lines per second including blanking.

Horizontal scan rate = vertical total × refresh rate

Pixel clock is the total number of pixels per second including blanking.

Pixel clock = horizontal total × vertical total × refresh rate

See also: Common pixel clock limits

What timing parameters should I use?

Use whatever works. Standards exist to make sure certain values always work so devices can operate with each other, but if you’re trying resolutions or refresh rates that the monitor doesn’t officially support, there’s no guarantee any particular timing parameters will work.

Common pixel clock limits

DVI

LinksLimitData rateBandwidth
Single165 MHz3.96 Gbps4.95 Gbps
Dual330 MHz*7.92 Gbps9.9 Gbps

* Technically no limit defined by the DVI specification, but often limited to 330 MHz.

HDMI

VersionLimitData rateBandwidth
1.0-1.2a165 MHz3.96 Gbps4.95 Gbps
1.3-1.4b340 MHz*8.16 Gbps10.2 Gbps
2.0-2.0b600 MHz14.4 Gbps18 Gbps

* AMD GPUs without HDMI 2.0 are limited to 297 MHz.

DisplayPort

DisplayPort limits depend on the number of lanes and the link rate:

  • Reduced Bit Rate (RBR) and High Bit Rate (HBR) are supported by all versions of DisplayPort.
  • High Bit Rate 2 (HBR2) is supported by DisplayPort 1.2 and newer.
  • High Bit Rate 3 (HBR3) is supported by DisplayPort 1.3 and newer.

4 lanes

Link rate8 bpc limit6 bpc limitData rateBandwidth
162 MHz (RBR)216 MHz288 MHz5.184 Gbps6.48 Gbps
270 MHz (HBR)360 MHz480 MHz8.64 Gbps10.8 Gbps
540 MHz (HBR2)720 MHz*960 MHz*17.28 Gbps21.6 Gbps
810 MHz (HBR3)1080 MHz1440 MHz25.92 Gbps32.4 Gbps

* NVIDIA Kepler GPUs are limited to 540 MHz.

2 lanes

Link rate8 bpc limit6 bpc limitData rateBandwidth
162 MHz (RBR)108 MHz144 MHz2.592 Gbps3.24 Gbps
270 MHz (HBR)180 MHz240 MHz4.32 Gbps5.4 Gbps
540 MHz (HBR2)360 MHz480 MHz8.64 Gbps10.8 Gbps
810 MHz (HBR3)540 MHz720 MHz12.96 Gbps16.2 Gbps

1 lane

Link rate8 bpc limit6 bpc limitData rateBandwidth
162 MHz (RBR)54 MHz72 MHz1.296 Gbps1.62 Gbps
270 MHz (HBR)90 MHz120 MHz2.16 Gbps2.7 Gbps
540 MHz (HBR2)180 MHz240 MHz4.32 Gbps5.4 Gbps
810 MHz (HBR3)270 MHz360 MHz6.48 Gbps8.1 Gbps

DVI specification

Digital Display Working Group (DDWG), the group that created the Digital Visual Interface (DVI) standard, doesn’t seem to exist anymore, so here’s an archived copy of the DVI specification:

https://www.monitortests.com/download/pdf/dvi_10.pdf

An interesting note is the DVI specification doesn’t actually specify a maximum pixel clock, only that pixel clocks greater than 165 MHz must use two links. In fact, it states the first link can operate beyond 165 MHz if the pixel clock is greater than 330 MHz.

FIX: BenQ XL2730Z and ZOWIE XL2730 missing 144 Hz refresh rate

If you have a BenQ XL2730Z or ZOWIE XL2730 and can’t set the refresh rate to 144 Hz because the option disappeared, it may be a firmware bug.

Follow these instructions to reset the monitor:

  1. Power off the monitor.
  2. Hold down buttons 3 and 4 and power on the monitor.
  3. Keep buttons 3 and 4 pressed until the picture appears.
  4. Press button 5 to enter the factory menu.
  5. Choose “CLEARUSER” to reset the monitor.
  6. Unplug the monitor’s power for a minute.
  7. Plug the monitor back in and power on the monitor.

Custom Resolution Utility (CRU) with older Intel GPUs

Custom Resolution Utility (CRU) 1.4.2 was recently released with a new feature that allows exporting self-contained EDID override installers. This includes an alternative method compatible with older Intel GPUs.


Use the “Export…” button:


Choose “EXE File” for the file type:


Run the .exe file:

  • Choose “Install EDID” to install the EDID override on all matching displays.
  • Choose “Reset EDID” to remove the EDID override.