Windows 8 has a problem – it really can boot up too quickly.
So quickly, in fact, that there is no longer time for anything to interrupt boot. When you turn on a Windows 8 PC, there’s no longer long enough to detect keystrokes like F2 or F8, much less time to read a message such as “Press F2 for Setup.” For the first time in decades, you will no longer be able to interrupt boot and tell your PC to do anything different than what it was already expecting to do.
Fast booting is something we definitely want to preserve. Certainly no one would imagine intentionally slowing down boot to allow these functions to work as they did in the past. In this blog I’ll walk through how we’re addressing this “problem” with new solutions that will keep your PC booting as quickly as possible, while still letting you do all the things you expect.
Too fast to interrupt
It’s worth taking a moment to watch (again, if you’ve already seen it) the fast boot video posted by Gabe Aul in his previous post about delivering fast boot times in Windows 8. In this video you can see a laptop with a solid state drive (SSD) fully booting in less than 7 seconds. Booting this fast doesn't require special hardware, but it is a feature of new PCs. You'll still see much improved boot times in existing hardware, but in many PCs, the BIOS itself (the BIOS logo and set of messages you see as you boot up) does take significant time. An SSD contributes to the fast boot time as well, as you can imagine.
If the entire length of boot passes in just seven seconds, the individual portions that comprise the boot sequence go by almost too quickly to notice (much less, interrupt). Most of the decisions about what will happen in boot are over in the first 2-3 seconds – after that, booting is just about getting to Windows as quickly as possible. These 2-3 seconds include the time allowed for firmware initialization and POST (< 2 seconds), and the time allowed for the Windows boot manager to detect an alternate boot path (< 200 milliseconds on some systems). These times will continue to shrink, and even now they no longer allow enough time to interrupt boot as you could in the past.
On the Windows team, we felt the impact of this change first, and perhaps most painfully, with our own F8 behavior. In previous versions of Windows (as far back as Windows 95), you could press F8 at the beginning of boot to access an advanced boot options menu. This is where you’d find useful options such as Safe Mode and “Disable driver signing.” I personally remember using them when I upgraded my first PC from Windows 3.1 to Windows 95. F8 helped me quickly resolve an upgrade issue and get started using Windows 95.
Continue at source:Designing for PCs that boot faster than ever before - Building Windows 8 - Site Home - MSDN