Windows 8 machines only take 10-15 seconds to boot up, with some switching on even faster depending on the SSD. But how have we gotten to this point? Microsoft engineers combined the hibernation and shutdown modes into one for Windows 8, and Windows 8.1 uses a hybrid boot mode that allows the PC to start up much more quickly. The kernel lets it hibernate instead of shutting down completely, and the use of cores makes it possible to start-up in seconds.