The driver that initialises your plug-in GPU is shipped in flash on the card, is signed by Microsoft, and won't run unless that signature validates.

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ThePowerOfFuet 3 days ago | parent | next [-]

I am reticent to argue with someone of your reputation, but AFAIK UEFI can initialize a basic framebuffer (and write to it) in a standardized manner without needing any ROM on the card.

https://wiki.osdev.org/GOP

	▲	mjg59 3 days ago \| parent [-]
		The GOP driver is provided by the card, and then exposes a standardised interface to the firmware.

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tsimionescu 4 days ago | parent | prev [-]

Doesn't that happen only after UEFI starts the boot process, and only if Secure Boot is enabled?

	▲	mjg59 4 days ago \| parent [-]
		I don't understand what "UEFI starts the boot process" means? The firmware is what initialises the hardware. If the code needed to initialise your GPU doesn't have a trusted signature then it won't be executed, and you won't have any working graphics, so you won't have a UI to let you disable secure boot. If secure boot isn't enabled in the first place then yes this isn't a problem.