What is Fast Startup in Windows 11 and why it can break dual boots and older BIOSes?

In this post we are going to talk about what Fast Startup is in Windows 11 and how it contributes to a fast system startupWe'll also look at why this same feature can break dual boots and older BIOSes, and what you can do to avoid these critical errors. Let's get to it!

What is Fast Startup in Windows 11?

One of the features that I like the most about Windows 11 es how little time it takes for the system to be ready for useSuch speed depends on several factors, not the least of which is the Fast Startup feature in Windows 11. But this feature can become a real headache for those using dual boot or an older BIOS. Why?

Let's start by defining what Fast Startup is in Windows 11. As the name suggests, it is a feature designed to speed up Windows 11 startupIt was introduced in Windows 8 and received significant improvements in Windows 10 and Windows 11; it's so effective that it comes enabled by default in the operating system.

How does Fast Startup speed up startup in Windows 11? Basically, what it does is combine elements of traditional shutdown with hibernationInstead of shutting down the computer completely, it retains some data from its current state and saves it to the hard drive. When you turn the computer back on, the system doesn't start from scratch, but instead uses that stored data.

What is a traditional shutdown in Windows 11? Differences with Fast Startup

To better understand what Fast Startup is in Windows 11, it is worth reviewing the process of a traditional shutdownWhen you click the Shut Down button, Windows typically follows this sequence:

1. Close all Applications.
2. Close all services y sessions of user.
3. The system commands the hardware to shut down, and the power is cut off.
4. Result: The computer shuts down completely. The next time you turn it on, it will have to load the kernel, drivers, and all services from scratch. This will be a cold boot.

For its part, Fast Startup in Windows 11 follows a similar sequence, but adds a step near the end of the process. When you click the Shut Down button with Fast Startup enabled, Windows performs the first two steps (closing apps, services, and sessions). However, Instead of shutting down the Windows kernel and hardware drivers, it runs a process similar to Hibernation.

Before shutting down the computer, the current state of the Kernel and drivers They are preserved in a file on the hard disk (hiberfil.sys)So, when you press the power button, Windows doesn't perform a cold boot. Instead of loading everything from scratch, it simply reads the contents of the hiberfil.sys file. So, what it does is restore the kernel and drivers to the state they were in before the shutdown.

Of course, The Fast Startup process in Windows 11 is much faster than starting everything from scratch.That's why the system boots so quickly, especially on computers with mechanical hard drives (HDDs). All of this works like a charm... unless you have an old BIOS or configure dual boot. Let's see why.

Why Fast Startup Breaks Dual Booting and Old BIOSes

Fast Startup in Windows 11 is one of the best features for getting your system to boot quickly. However, it also It can become a nightmare if your computer has an old BIOS.And the same thing happens when you want to use two operating systems (Windows and Linux, or another Windows) on the same computer. Why is this?

On dual boot computers it is common to have shared folders that can be read and modified from both operating systems. For example, a Documents folder where you save and delete files from both Windows and Linux. But with Fast Startup enabled in Windows, you almost certainly won't be able to modify (or even read) anything in that folder from Linux. Why?

As we mentioned, the Fast Startup feature doesn't shut down your computer in the usual way. Instead, it locks the disk's file systems (usually NTFS) in a specific state and marks them as "in use." Then, When Linux tries to access the same partitions as Windows, it finds them locked.At most, it mounts them as read-only; at worst, the system crashes on boot.

And the other way around can also cause problems. If you modify files from Linux and then boot into Windows, you may experience data corruption or boot errors. Tasks as simple as Sharing files or updating documents becomes impossible to doAnd all because you have the Fast Startup feature enabled in Windows 11.

The problem with old BIOS and Fast Startup in Windows 11

Fast Startup in Windows 11 can also cause issues when your computer's BIOS/UEFI is older. This makes sense, because Fast Startup depends on modern energy states, such as Modern Standby OS (if you are interested, see the topic Modern Standby drains battery during sleep: how to disable it). Older BIOSes do not support this technology, which can result in:

• Loop reboots or failures to boot, because it does not recognize the “restore” command that Windows sends after hibernation.
• Unable to access BIOS/UEFI: The boot process from hibernation is so fast that it doesn't detect when you press the key to enter the BIOS (F2, Del, F12).
• Errors with peripherals and booting from USB: The BIOS may not load drivers for peripherals and external drives correctly.

Solution: Disable Fast Startup in Windows 11

If you are having issues with Fast Startup in Windows 11 due to dual booting or having an old BIOS, the solution is disable it. As we mentioned, this feature is enabled by default in most Windows 11 installations. To change it, follow these steps:

1. Go to Control Panel – Power Options.
2. Click Choose the behavior of the power buttons.
3. Tap “Change settings currently unavailable.”
4. Uncheck the box labeled “Turn on fast startup (recommended).”

This disables a legacy feature from a time when HDDs delayed the boot process. Now, With the arrival of SSDs, it is not as necessary to keep Fast Startup active. to enjoy a fast startup. Especially if you're using two operating systems on the same computer or have an older BIOS. There you have it!