Lenovo x250

Great laptop, awful screen; from stock it has a TN 1366x768 display which performs very badly so when a white circle appeared in the middle of the screen I knew it was time to buy a better one. 

The chosen one is a FHD IPS LCD 1920x1080 screen (that can be bought from here) replace the screen is quite simply and you can find many videos on Youtube about it. So let's skip this step.

Lenovo uses in their BIOS a whitelist, a whitelist is a list of all the allowed components that can be installed on your laptop, this way Lenovo controls which brand and which model are allowed. As you guessed the main problem with this screen is that is not contained in the whitelist.

The screen works fine on Linux, but on Windows you can't change brightness.

So, how does the computer know that the screen I'm using is not in the whitelist? It check the EDID (Extended Display Identification Data) of the display.

From here we have 2 solutions:

1.- Clone the original screen EDID into the new one.

2.- Add the new EDID into the withlist.

Well I tried the first one, but the screen EDID was write-protected and couldn't find more information.

Solution 2

So, for this solution we are going to need an eeprom programmer, a good one is the CH341 CH341A USB programmer with the clamps.

Programmer

Clamps

And for the programmer I like Asprogrammer. Before disassembling our laptop let's start by retrieving the EDID of the screen. [The new screen have to be already connected]

Screen EDID



Use Monitor Asset Manager Software to get the EDID of your display. Select your display on the left list and then go to File and save as binary.

Laptop disassembling

Now, you need to remove the screws from the bottom of your laptop and remove the plastic cover. Don't forget to remove the battery and disable the internal battery in the BIOS.


Then you need to create a backup file, so put the clams on the chip, as it follows.

AsProgrammer

The user interface is quite simple, you will only need 4 buttons: "Read ID", "Read IC", "Erase IC" and "Programm IC".

When everything is setup, click on "Read ID" and a small pop-up window will appear displaying the your eeprom chip model, if you get a message like the one shown in the picture below, try to reposition the clamp. It may takes several tries until you get it right.

User Interface

Bad reading output, try to get a better grip with the clamps

First, we are going to create a backup copy. Click on "Read IC" and the programmer will start retrieving the information, after it is done, save it and repeat the process. Once you have 5 copies use HxD to compare them, if there is no difference between the files your readings are good.

Bios Modification

To modify the Bios I asked for Klem's help on this website. You will need to send him the bios file and the EDID binary file generated above. 

Bios Update

Now open the modded Bios file with Asprogrammer, click on "Erase IC" and then "Programm IC".

Bios Configuration

Finally, some tweaks have to be done on the Bios Setup Menu:

Update

I just discovered that UEFI tool is used to modify BIOS files, I'm trying to learn how does it work, I will post further updates in the future.