On some level, the BIOS has to determine if new chips have appeared on the bus. But also check that conditions haven't changed. If you took out a RAM stick and

On some level, the BIOS has to determine if new chips have appeared on the bus. But also check that conditions haven't changed. If you took out a RAM stick and inserted it into the same slot, the conditions (due to dust, moisture, difference in seating) could be enough to throw off the reliability of the training data. So at minimum it has to verify the settings to be correct.