I did this once on an Acer monitor. I was modifying it to strobe the LED backlight to give blur-free video like a CRT. I had found that the DDC bus exposed other registers to control the backlight, etc. and had an external circuit connected to do the strobing. I noticed it had registers to read and write the flash ROM, so I dumped it, wrote an 8051 disassembler and did some crude reverse-engineering, then eventually modified the ROM to include a strobed mode (occupying the lower end of the brightness control, so it could enabled and adjusted via the OSD or normal DDC brightness controls). I did have to go inside and connect the write line when flashing it. There was conveniently an interrupt on vblank, and the timer that controlled the LED backlight had a mode that could turn it on a little before the next interrupt and then off an adjustable amount of time after, just the right time needed to flash it on after the LCD had settled updating. Originally I just wanted to remove the several-second boot logo (which I achieved).

The flash chip usually has a write enable/disable pin and most monitors and TVs will wire it to prevent writes to the EDID. I would guess only cheap ones don't bother. It's risky as without protection, a voltage glitch during a read can turn it into a write and trash the flash.

The author recommends using a Pi while noting it's not a requirement

>If you attempt these commands on a PC, it’s possible that you could accidentally flash hardware that isn’t an EDID, like a RAM module’s SPD EEPROM.

> the same process works to modify the edid stored on a typical monitor

That would be a strange oversight by the hardware developers.

Typically they would buy pre-programmed EPPROMs and then place it on to a board where the write enable pin is never pulled high.

It would be strange to put an EEPROM into a product like a monitor and leave it writable, but I’ve seen stranger things on shipping hardware.