Microsoft (in particular, Emily Wilson) demonstrated the launch speed of Windows 8:
It is explained by such a quick launch by introducing into the hibernation mode of the system core. The user session, in turn, closes fully. Compared to full hibernation, which consumes all available RAM and is rather slow, such use of the mode does not impose special hardware requirements, but allows you to load the operating system 30-70% faster with the detection of new devices and drivers (the performance increase depends on the hardware system ).
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As I understand it, 70% acceleration is achieved when using an SSD, while 30% is on a normal HDD.
PS The old cold start mode will remain available for use.