Comment by numpad0

Backlights, battery, anything. Modern high performance CPUs need an external debug adapter to set up the board before they can be powered on(old supercomputers did too). Blobs running on a less-modern CPU handles that. The less modern CPU in RasPi is its GPU, but it can be other devices; it can be the modem, or a "security" sub-CPU.

IMO it's possible that the bigger issue is no one knows what's going on inside these devices. Maybe some of blobs aren't needed, or they can be readily replaced, etc., but no one has time to deal with it. This is probably a field that cheap brain-hours that LLMs just created could actually revolutionize.