ID_SD and ID_SC pins
- You can't use GPIO 0/1 as an I2C bus on the Pi3. On the Pi3 I2C bus 0 is used internally.
- You can use GPIO 0/1 as ordinary inputs and outputs on the Pi3.
- There are no restrictions on earlier Pi models, you can use GPIO 0/1 as ordinary GPIO or as an I2C bus.