What is Laptop LCD Screen EDID?

You may have heard the term EDID used by laptop screen suppliers, you may have purchased a screen that appears to physically fit, or may even look identical to the original but fails to function correctly.

Believe it or not, the same model of laptop screen can come in different hardware and software versions. Hardware versions may denote subtle differences like Matte or Gloss or the position of a connector for the LVDS LCD cable; The software or firmware version is known in the industry as EDID or Extended Display Identification Data. The screen has it's own mini operating system that runs on the panel and communicates attributes and settings to the laptop's BIOS and Operating System.

EDID is a VESA display standard format that contains basic information about the screen and it's capabilities including information about the manufacturer, resolution, orientation, colour characteristics and factory timings such as response rates and refresh frequencies. The display's name is included and serial number and also other custom settings that may be specific to it's type of usage. Some manufacturers may request LCD screens from the LCD manufacturers with modified EDID and then program the laptop's BIOS to only recognise the modified screens and no other versions.

For example, DELL may take a model of screen that is used in HP laptops, and modify the EDID for a specific purpose, so the screen functions in a different manner in their laptops. This then makes the 2 identical screens incompatible with each other, you need one for DELL and one for HP. So screen FW (firmware) numbers then become important to the LCD suppliers when supplying screens for different brands.

Communication between the LCD screen and the laptop is made via the LVDS (LCD data DDC cable) cable, and usually one of the connector pins (2nd from last is normal) is used for EDID signalling. The laptop's BIOS will request EDID information and the screen will supply it, via a handshake type data transfer, who are you? I'm LP156WH2 TLA1 EDID version 1.3, 1366x768, 65hz, etc. Then the laptop's BIOS confugures the screen and begins video transfer. The boot up process starts.

Incorrect EDID information or missing EDID information can result in screens staying blank, lighting up white, or displaying odd or inverted colours. The image can be chopped into 4 copies or split or scrambled or not fit on the screen as though the resolution is wrong.

The Windows display drivers and monitor INF files can also override the EDID settings and cause problems.

Transferring EDID between screens

EDID can be transferred between screens of the same make via an LCD burner connected to a PC's USB connection.