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Enable or disable AHCI mode in Windows. AHCI or IDE - which is better? Description of the mode, characteristics

At one time, hard drive developers were looking for various ways to improve the performance of the disk subsystem, which remained relatively slow from year to year, and progress in the storage environment consisted mainly of increasing HDD capacity. Gradually, the SATA standard and corresponding versions of this interface appeared, which brought some new technologies.

In fact, there are only two common technologies - “Hot Plug”, that is, hot-swappable drive and “NCQ” (Native Command Queuing), a native (innate) command queue. The first technology is quite simple, it allows you to simply remove drives “on the fly” without turning off the computer, although for this you still need to use their software shutdown. NCQ was able to add speed to hard drives, and even more so, it will be able to do this with SSDs, which cope well with “deep queues”.

These, as well as some other options, will work if the drive controller is set to SATA AHCI mode. In turn, AHCI (Advanced Host Controller Interface) is an advanced controller operating system that is only available in this (AHCI) operating mode.

The good news is that all modern platforms support the AHCI mode of operation of the internal SATA controller, and it can be easily selected in the settings of the main EFI or BIOS shell.

The bad news: if the operating system was installed in normal "IDE" controller mode, it will not boot and will freeze after selecting AHCI and attempting to start. That is, you may need to reinstall the operating system. Moreover, to install Windows XP (which, however, is not recommended when using an SSD), you will need to have AHCI drivers in advance, otherwise the OS will simply be impossible to install.

Important: You can enable AHCI support on Windows 7 without reinstalling the OS. To do this, before switching the controller to AHCI mode, you need to go to the registry editor.

Editing a registry setting.

  • Call the command line (ALT + R) and write “regedit”, of course, without quotes;
  • Find the registry key “HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci »;
  • Find the “Start” option and double-click on it. In the "value" field, enter "0". That's it, the system can be restarted and set to AHCI mode.

So does it make sense to use the AHCI mode of the SATA controller? There is definitely a point. Let's take a quick look at the benefits again:

  • Support for hot-swap drives;
  • Overall productivity increase from NCQ technology;
  • Operation at maximum speeds (relevant when using a controller and SSD SATA-600);
  • Support for additional commands, such as TRIM.

Yes, the TRIM command will only work on the operating system installed on the drive running in AHCI controller mode. You can learn about the importance and usefulness of this command. So there is no reason to use the controller's standard IDE compatibility mode.


Hard drive manufacturers are constantly looking for ways to speed up their products. Relatively recently, storage disks for computers worked in a rather slow mode and their development concerned only an increase in the total volume of the storage medium. Then developers invented a completely new type of SATA interface, which allowed access to the latest types of hard drive acceleration.

The main innovations were the following 3 functions:

  1. NCQ (Native Command Queuing) - built-in support for command execution order. This function is designed to speed up the operation of the HDD. But significant performance is achieved on SSD (Solid State Drive) type hard drives, which are known for their high performance due to fast processing of command execution sequences.
  2. Hot Plug - translated from English means “hot plug”, which should be understood as replacing the hard drive without turning off the computer. You just need to disconnect the disk using software (like a flash drive). This function may be of interest to users who constantly work with several media at the same time. This will allow you to quickly change hard drives without stopping work on your computer.
  3. TRIM - translated from English as “trim”, that is, this function allows you to delete files or format your hard drive without causing harm. As you know, during such operations the disk wears out faster. This technology is relevant for modern SSD media, as it was created in order to be competitive with conventional HDDs. An SSD with this feature has excellent operating speed and durability.

But for all these features to become available, you will need to configure the SATA interface to a special AHCI mode in the BIOS.

What is AHCI?

AHCI (Advanced Host Controller Interface) is a development by Intel, which is designed to replace the interface of the long-outdated ATA controller. The main reason for the replacement is its inability to support command queuing and hot-swapping functionality.

Not all motherboard chips support the AHCI function. In some cases, the board chip provides AHCI support, but it may not be implemented in the BIOS itself and will simply not be available. This problem can be resolved by updating the BIOS firmware. In addition, you can try to update the BIOS with unofficial firmware, but this is done at your own peril and risk, since there is a possibility of damaging the motherboard.

Until today, the main problem is changing the interface from ATA to AHCI (Blue Screen Of Death - abbr. BSOD). At the same time, at the very bottom of the BSOD the message STOP 0x0000007B, INACCESSIBLE_BOOT_DEVICE was displayed. It was possible to eliminate the blue screen only by undoing all previous actions in the BIOS or reinstalling the Windows operating system. It later turned out that the reason for this was the lack of drivers that are required for AHCI to function.

Switching the SATA interface to AHCI mode before installing the OS

Selecting the SATA operating mode in the BIOS from Phoenix

Before, you need to change the SATA configuration in the motherboard BIOS. This can be done by pressing the F2/Del key after turning on the computer. Typically, the SATA Configuration option is located in the Advanced section, but its name may vary depending on the BIOS. You need to find it and enable AHCI controller mode. Save the settings (Save and Exit) and restart your computer.

Switching the SATA interface to AHCI mode on an existing OS

On an already running Windows 7, you need to shut down all applications and launch the Run command by simultaneously pressing the Win + R keys (the Win key is usually indicated by the Windows logo). In the window that appears, type the regedit command to open and click OK. A registry window will appear in which you need to open the section along the path: HKEY_LOCAL_MACHINE\System\CurrentControlSet\services\msahci.

In the directory that opens, you need to change the value opposite Start to 0 and save the registry settings. Then restart your computer and enable AHCI mode through the BIOS, as described in the previous paragraph. After booting the Windows system, you need to reinstall the SATA drivers, which are usually located on the disk that came with your motherboard or laptop. If everything is done correctly, Windows will detect the new hardware and install it.

Along with the above features, you will get full SATA III bandwidth, which is 6 Gb/s.

Automatic transition of Windows 7 and 8 to AHCI or RAID mode

Due to the fact that switching to AHCI mode caused many problems for Windows users, Microsoft has developed a special utility that allows you to prepare the operating system for changing the mode to AHCI or RAID. It can be downloaded from the official Microsoft website. After launch, the utility itself will perform all the necessary actions. You just need to restart the system, simultaneously switching to AHCI mode in the BIOS. In the future, Windows itself will install the necessary AHCI drivers for operation.

In Windows 8, just switch to AHCI mode in the BIOS and boot the OS in safe mode. If you were unable to start the system in safe mode, you can open the Run window using Win + R and enter the msconfig command. In the “Boot” section, you must check the “Safe Mode” item, while selecting the “Minimal” option. After this, the system will boot into the desired mode and install the AHCI drivers.

AHCI mode is supported in Windows operating systems starting from Windows Vista. In older versions of the OS (such as Windows XP, etc.), there is no built-in support for AHCI mode and for this mode to work, you must install additional vendor-specific drivers.

However, not everything was smooth with the activation of AHCI mode in the new Microsoft operating systems. If the system was installed in normal (IDE) mode, the AHCI driver in the system is located in disabled condition. This leads to the fact that on such systems, when AHCI mode is enabled on a SATA controller in the BIOS, the system stops seeing the sata drive (the necessary ahci driver is missing) and crashes into BSOD ( INACCESSIBLE_BOOT_DEVICE). For this reason, controller chipset manufacturers (primarily Intel) recommend enabling AHCI mode BEFORE OS installation, in this case the installer understands that the chipset supports AHCI mode and installs the necessary drivers (for some chipsets, it is sometimes necessary to load specific AHCI/RAID drivers directly during the Windows installation process, for example, from a USB flash drive or CD/DVD drive).

Note. Mode AHCI (Advance Host Controller Interface) Enables advanced SATA features such as hot plugging ( Hot-Plugging) And NCQ(native command queuing), which improves the performance of disk operations.

In Windows 8, the situation with activating AHCI has not changed, and if you try to change the SATA controller mode to AHCI without making changes to Windows itself, this will lead to the inability to boot from the system disk. The fact is that Windows 8 also does not automatically load the AHCI driver for a controller that was not in AHCI mode at the time the system was installed.

The article is intended for those who installed Windows 8 in IDE mode and would like to switch to AHCI mode without reinstalling the operating system. If the BIOS (or) is already set to AHCI mode, then there is no need to do anything additional - your Windows 8 already supports AHCI mode.

We have already described without reinstallation. According to this article, on Windows 7 running in normal (ide) mode, you need to switch the standard AHCI driver to automatic loading mode (the driver is called msahci) and only then activate AHCI in the BIOS. The procedure went quite smoothly and in the vast majority of cases painless.

In Windows 8 (and Windows Server 2012), when trying to enable AHCI mode in this way, the user will encounter a problem: the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci branch is simply missing in the registry. And trying to create it manually will lead to nothing.

The fact is that Microsoft decided to change the name of the driver responsible for supporting AHCI mode for SATA controllers, replacing it with a new driver called StorAHCI. It is worth noting that this driver has the same functionality and supports the same devices as MSAHCI.

We were able to discover two ways to activate AHCI after installing Windows 8. One of which is related to modifying the registry, the second is related to booting in safe mode.

Enable AHCI in Windows 8 using the registry

To enable AHCI mode in Windows 8 without reinstalling the system (which was installed in IDE mode), you need to make changes to the system registry.

Note: once again we remind you that the specified modification of the Windows 8 registry must be done BEFORE enabling AHCI in BIOS.

Unfortunately, the specified method for activating the ahci driver in Windows 8 does not always work (it does not work in about 10-20% of cases). In this case, it is recommended to use the official instructions from Microsoft, available in the knowledge base article KB2751461(http://support.microsoft.com/kb/2751461).

An alternative way to enable AHCI in Windows 8

In the event that the above method did not work, and Windows 8 does not boot in AHCI mode, going into BSOD or endless attempts to restore Windows (Attempting repair). Necessary

  1. Disable AHCI mode in BIOS
  2. Undo changes to the system registry by setting ErrorControl = 3 And StartOverride\0 = 3
  3. Using the following command, we will set Windows 8 to boot in safe mode - Safe Mode (as an option, you can). bcdedit /set (current) safeboot minimal
  4. Then you need to reboot the system, enter the BIOS again, switch to AHCI Mode and save the changes.
  5. As a result, Windows 8 should boot into safe mode and automatically install the AHCI driver.
  6. Then you need to disable booting in SafeMode: bcdedit /deletevalue (current) safeboot
  7. And restart Windows
  8. The next time you boot the system, the system should boot normally. All that remains is to make sure that the AHCI controller appears in the device manager.

To make sure that the performance of the Windows 8 disk subsystem has increased due to AHCI mode, run the update and check that the Disk data transfer rate has increased. In our example from 5.2 to 8.1 units (although to be frank there are more 🙂).

This is a new SATA mode to work with devices memory type. Only in it can a computer fully use all SATA capabilities, or rather:

  1. Quick replacement hard drive. And in more detail, this means that it can be changed without turning off the computer. When working with servers it is very comfortable.
  2. NCQ– thanks to this technology, the number of movements of the heads that perform reading is reduced significantly. Thereby speed hard drive usage increases when it is used by several programs at once.

If activate Achi, then you will quickly access files that are stored on ROM, and the computer will also work much better faster. Of course, the increase will not be noticeable on a regular home PC. However, if support for this option is available, then it would be better if you enable it.

IDE mode - what is it?

This is too much outdated technology that was popular in the nineties and early two thousand. It was introduced in the IBM PC - the first computers. In it, data transfer took place on speed 150 Mbit per second. Many popular technologies didn't support. For example, it was impossible to remove the hard drive or CD drive without rebooting the PC. Then these features were added, but not every computer could use them. However, it is still in use today.

How to enable ACHI/IDE mode

Switching between ACHI and IDE occurs through BIOS. This is done before installing Windows, as follows:

In Windows 10 you can instantly switch on Achi, for this:


Which mode is better

Of course, it's best to choose ACHI. And this can be understood by comparing the two modes. IDE should be chosen if on your system no drivers to SATA. All modern PCs support SATA, that is, if you select IDE, it will occur emulation, and this will not give any increase in performance, which is not what we need.

Proper operation of a computer is possible only with coordinated interaction between the hardware and the operating system. Technology is evolving, and lately this has been most noticeable in the field of storage. Modern hard drives and SSD drives are many times faster than those used in computers 5-10 years ago. For data transfer, the SATA interface is used, through which the drive is connected to the computer. The SATA interface is capable of operating in two modes: IDE and AHCI, and if you have a modern hard drive or SSD installed, you can speed up your computer by enabling AHCI mode.

What is AHCI mode

As noted above, AHCI is one of the data transfer modes over the SATA interface. As you know, through the SATA interface you can transfer information at speeds from 1.5 to 6 Gigabytes per second. The maximum speed is supported in AHCI mode, which should be used with all modern drives. As for the IDE mode, it is supported in the SATA interface for compatibility with older hard drives.

By default, AHCI mode is not always enabled in the Windows operating system, even if the drives are connected to the motherboard via SATA. Because of this, the user loses in computer performance, since the disk speed is limited by software. By setting the AHCI mode, you can increase the speed of the drive by 20-30%, which will affect the overall experience of the computer.

How to find out if AHCI mode is enabled in Windows

Most often, users do not even suspect that it is necessary to enable AHCI mode in order to improve computer performance. At the same time, Windows by default does not always work with HDDs and SSDs, even the most modern ones, in AHCI mode. To check if AHCI mode is enabled in Windows, you need to do the following:


Note: Also, the absence of devices operating in AHCI mode in the list may be due to the fact that old drives that are not capable of operating in the new mode are connected to the motherboard.

You can also check whether the SATA interface works in AHCI or IDE mode through the BIOS. To do this, you need to restart the computer and press “Del” or F2 during the boot process. The BIOS will launch, where you will need to find the SATA Mode item and see whether the AHCI or IDE option is installed.

Important: If you notice in the BIOS that the SATA interface is set to work in IDE mode, you do not need to switch to AHCI mode, since this will not do any good.

How to enable AHCI mode in Windows

Microsoft began supporting AHCI mode in Windows operating systems with Windows 7. However, you can enable it in Windows XP if you download the necessary drivers on the Internet, made by enthusiasts, and install them. However, it is worth noting that this method does not always provide a performance boost, and on Windows XP it is better to abandon the idea of ​​​​using AHCI mode and work with drives through a standard IDE.

To enable the AHCI mode itself, just set the appropriate setting for SATA in the BIOS. But this must be done before installing the Windows operating system, otherwise when booting the computer will display error 0x0000007B INACCESSABLE_BOOT_DEVICE or go into a constant reboot state. Therefore, to switch the IDE mode to AHCI when Windows is installed, you need to make some changes to the registry; below we will look at what actions to perform for each version of the operating system.

How to enable AHCI mode in Windows 10

In the modern Windows 10 operating system, Microsoft did not offer a setting that would enable support for AHCI mode on the fly if the SATA interface previously worked through the IDE. To correctly switch to AHCI mode, you will need to do the following:


After the computer boots, the Windows operating system will prompt you to install the necessary drivers to work with AHCI mode; be sure to do this.

How to enable AHCI mode in Windows 8 and Windows 8.1

To switch the Windows 8 or Windows 8.1 operating system to work with AHCI mode, you need to do some work on the command line. You will need to do the following:


It is worth noting that if the computer runs on an Intel CPU, then you can use the company’s standard utility, which allows you to make the necessary settings to switch Windows to work with AHCI. This is done as follows:


Note: The above method is only suitable for computers with Intel processors; there is currently no such solution for AMD.

How to enable AHCI mode in Windows 7

In the Windows 7 operating system, the method for enabling AHCI mode is close to that used in Windows 10. Here you will also need to make some changes to the registry as follows.