If the computer cannot locate the OS in the first device, it looks in the second and so on. Although computers typically boot from the main storage drive (HD or SSD), the first boot sequence ...

1] Using the hardware key combinations Make sure that your Surface device is completely shut down ... Release the Power button as soon as the boot logo shows up but keep holding the Volume ...

Boot process is the process in which any SoCs takes various device configurations (trim bit, device security settings, boot vector location) and memory initialization (like FLASH/SRAM/GRAM) is done ...