It differs between the different camera sensors. With CCD sensors, there were switchable amplifiers, but sometimes camera companies added software-pushed sensit

It differs between the different camera sensors. With CCD sensors, there were switchable amplifiers, but sometimes camera companies added software-pushed sensitivities. The most modern CMOS sensors are called ISO-less as the higher ISOs are implemented not by changing the amplification, but by digital post-processing. So for a wide range of exposures, there is little difference between higher ISO settings and pushing in post-processing. There might be some slight differences after all, as the in-camera processing might vary as well as some low bits skipped at low ISO values.