If it’s physically impossible to write to a ROM (read-only memory) cartridge, how do manufacturers do it?

Question

Is somehow locked physically during production, or through software?

In: 210

Answer 1

It used to be very common to use lasers on a microchip before it was packaged. You would test the microchip and based on the test results, pass coordinates to a laser telling it where to burn. This gave you the opportunity to fix bad chips or program customer specific information.
This is still done at a lot of companies that use older manufacturing processes.
The switch to EEPROMs and similar methodologies has happened in the last 20 years.