A friend of mine recently got a new Windows 8 system and
after using it for a couple of weeks sent me a list of questions that she had
about some of the features in the new operating system. She also had quite a
lengthy list of questions about features that she had been used to using in
previous versions of Windows, which were either no longer available or changed
in some way in the new version. While I was able to answer all of the questions
to her satisfaction, one set of related questions stood out for me.

She asked me why the default Power menu had both Sleep and a
Shut down commands, as shown in Figure A.
“Aren’t these operations the same thing in Windows 8 with its new Hybrid
Shut/Fast Boot feature?”, she asked. And, isn’t Fast Boot essentially
Hibernate?

Figure A

By default the Power menu has Sleep and Shut down commands.

As I pondered the answers to these questions, I realized how
difficult it could be to describe. I also realized how easy it is to be
confused by the whole thing and thus I decided to write this article.

Overview

The goal of Fast
Boot
is pretty obvious from its name – Windows 8 boots up faster than
previous versions of the operating system ever did. To accomplish this feat,
Windows 8 doesn’t totally shut down when you click the Shut down command.
Instead it only partially shuts down and partially hibernates. This is the
Hybrid Shutdown part of the equation. Then, when you turn on your computer,
Windows 8 starts very quickly because it only has to partially boot up and
partially wake up. This is the Fast Boot part of the equation. Fast Boot also
gets a boost from the efficiency of today’s hardware; namely UEFI (Unified Extensible Firmware Interface)
and multi-core processors.

To understand how all of this works, we really have to build
a foundation of knowledge. Of course, when you really dig into all the nuts and
bolts of this system, it gets very technical. However, in this article, I’ll
just give you the basics in fairly general terms.

A cold boot operation

Let’s begin with a basic understanding of how a computer
boots up from a complete shut down. There are essentially three stages that a
computer goes through as it boots up. When you turn on a computer, the first
thing that happens is the system’s firmware boots up and gets the computer
hardware ready for the operating system. Next, the operating system boots up
and gets everything ready for the user. Then, the user logs in and the
operating system sets up the user’s environment so that the user can launch
applications and get to work. If we simplify these stages, we have what I’ll
call the hardware session, followed by the kernel session, and then the user
session.

A shut down operation

As you can imagine, a shut down operation essentially works
in reverse. But for the sake of being complete, let’s cover it anyway. When you
shut down Windows, the user session shuts down first, then the kernel session
shuts down, and finally the hardware session shuts down.

A Hibernate operation

Since a big part of Fast Boot builds upon the Hibernate
feature, let’s take a brief look at how the Hibernate feature works. If you used
the Hibernate feature in previous versions of Windows, as shown in Figure B, then you know that a system coming
out of hibernation boots up faster than a system that is performing a cold boot, i.e. a system that starting
up from scratch after being completely shut down.

Figure B

The Hibernate command on the Shut down menus of Windows XP
and Windows 7.

The reason for this is that when you hibernate your computer,
the operating system doesn’t really shut down. Instead, it saves the current system
state and the contents of memory to a file called hiberfil.sys and then it shuts
down the computer – the hardware. Later, when you turn on, or resume, the
computer, rather than performing a cold boot of the entire system, the
operating system reads the contents of the hiberfil.sys and then restores the system
state and memory to the exact same condition they were in when the system went
into hibernation. This restoration, or resume, operation can occur much faster
than a computer can boot up from a complete shut down.

Of course, resuming from hibernation comes with a “your
mileage may vary” clause. The reason being that the speed with which the
system resumes depends on how big the hiberfil.sys file is. And the size of the
hiberfil.sys depends on how many applications were running and how much data
was in memory at the time that the system went into hibernation. For example,
if you hibernate your system when you have Word, Excel, and PowerPoint running
and files open in each application, the hiberfil.sys file is going to be larger
than if you closed all your apps before you hibernate your system. If the
hiberfil.sys file is larger, resuming is going to take longer. Even so,
resuming from hibernation is generally faster than booting up from a complete
shut down.

Knowing that people liked how fast their computers resumed
up from hibernation, Microsoft decide the figure out to make the process
better.

Hybrid Shutdown

Okay, now we have a good foundation with which to understand
how Fast Boot works. While the name Fast Boot implies a faster startup routine,
the magic actually begins at shut down using a technique Microsoft has called Hybrid
Shutdown. When you select the Shut down command from Windows 8’s Power menu,
the first thing that happens is that the user session shuts down just like in a
regular shut down operation. However, instead of closing the kernel session,
Windows hibernates the kernel session. Then, the hardware session shuts down
normally.

Shutting down the user session is quicker than hibernating
it, which is an improvement over the old hibernation operation. And,
hibernating the kernel session is quicker than shutting it down, which is an
improvement over the old shutdown operation. So, these two operations combined allow
Hybrid Shutdown to shut down Windows 8 faster than previous versions of Windows.

Fast boot

When you turn on the computer, the first thing that happens
is the system’s firmware boots up and gets the basic computer hardware ready
for the operating system. On a modern Windows 8 computer, the establishment of the
hardware session is a much quicker operation than on older systems because the
UEFI system is much more efficient than the BIOS system. To complete the
hardware session, the operating system enumerates all available hardware and
loads the appropriate drivers, thus ensuring that a solid hardware session is
available.

Once the hardware session is ready, the operating system
begins its resume operation. Since the resume operation consists only of restoring
the kernel session, rather than restoring both the kernel session and the user
session, the resume operation can occur much quicker. In addition to this, the
resume operation gets a boost from the fact that the operating system is now
designed to take advantage of multiple CPU cores when it comes to processing
the hibernation data file. (The old resume process only used one.) If your
Windows 8 system is installed on an SSD, you can expect an even more responsive
resume operation.

Performing a real shut down in Windows 8

At this point my friend was wondering, if selecting the Shut
down command from Windows 8’s Power menu performs a hybrid shutdown, rather
than a real shut down, how do you get a fresh kernel session – in other words
how do you achieve a real cold boot? Well, when you click Restart you will
indeed get a full reboot of the system and thus a fresh kernel session.

You can also achieve a real shut down using the Shutdown
command line tool. To do so, you can open Command Prompt and type the following
command:

J­vŒ'þÏí

If you want to have regular access to a real shut down
procedure, you can use this command line in a shortcut.

Sleep and Hibernation modes

In Windows 8, Sleep and Hibernation work pretty much the
same as they did in previous versions of Windows. Selecting the Sleep command
from the Power menu, essentially pauses the operating system, puts your work
and settings in memory and then puts the entire system in a low power
consumption state. Pressing any key will instantly revive the system and you
can get back to work right where you left off.

While it doesn’t appear on the Power menu by default, you
can add Hibernate from the Power Options | System Settings screen shown in Figure C. When you do, selecting the
Hibernate command puts the system into hibernation mode just like I explained
earlier.

Figure C

You can add the Hibernate command to Windows 8’s Power menu.

What’s your take?

Now that you know how it works, what do you think about
Windows 8’s Hybrid Shutdown and Fast Boot features? As always, if you have comments or information to
share about this topic, please take a moment to drop by the TechRepublic
Community Forums and let us hear from you.

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