[decided] Switching ACHI <--> IDE in Windows 7, 8, 10 installed

AHCI mode of SATA hard drives enables the use of NCQ (Native Command Queuing) technology, DIPM (Device Initiated Power Management) and other features such as hot-swappable SATA drives. In general, enabling AHCI mode allows you to increase the speed of hard drives and SSDs in the system, mainly due to the advantages of NCQ.


There are several modes of operation of modern Serial ATA controllers (SATA): IDE, AHCI, RAID. AHCI mode is generally more powerful than IDE. Sometimes there are situations when you need to change the mode of the controller without reinstalling the OS, but with a different mode of the controller the system does not want to load. The problem is that when Windows starts up, it only loads the necessary drivers, and the drivers for the IDE and AHCI modes are different … The solution to this problem is to include the necessary drivers in the list of drivers to be loaded by modifying the system registry.

Open the registry editor, go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\ and then change the start mode for the necessary drivers:


Controller mode change from “IDE” to “AHCI” (shown if there is a modern screw with NCQ support)
The value of the “Start” parameter (Type: REG_DWORD) must be changed to “0” (see following figure) for the “msahci”, “Iastor” or “IastorV” drivers.

Iastor & IastorV – Intel Matrix Storage Manager drivers.
After that in the BIOS you can change the mode of the controller from “IDE” to “AHCI”.

Controller mode change from “AHCI” to “IDE” (shown if the hard drive in AHCI mode operates in very slow “Multi-Word DMA Mode 2” DMA mode, )
Change the value of the “Start” parameter (Type: REG_DWORD) to “0” (see figure below) for the “pciide” driver.

(there was also a case that had to be changed in the section HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\intelide).

After that, you can change the operating mode of the controller from “AHCI” to “IDE” in the BIOS. Enabling autoload for this driver helped to solve the problem with “Multi-Word DMA Mode 2” without changing the mode to IDE, and now you can honestly enjoy the hard drives in “Ultra DMA Mode 5” mode.

Bear in mind that the list of controllers and their drivers is much wider and maybe it is your case that you need to enable some other driver, take a closer look at the list of drivers in the HKEY_LOCALMACHINE\System\CurrentControlSet\Services.

Go to your computer’s BIOS or UEFI.

  • Find there an item “Storage options”, “SATA Mode”, “SATA Emulation” or another very similar name.
  • If the value of this item is “AHCI”, then the AHCI mode is already in use.

/></p><ul><li>If there is a value <b>“IDE”</b> in the specified item, do not hurry to change it to <b>“AHCI”</b>.</li><p>.</ul><p>The thing is, if after installing Windows you just turn on AHCI mode, you will see a BSOD <b> error INACCESSABLE_BOOT_DEVICE</b> (which many people know as the “blue screen of death”) or the system will refuse to boot, performing a cyclic reboot. It is therefore recommended that you enable AHCI before installing Windows.</p><p>As soon as you reboot, the operating system will start installing SATA or IDE drivers, and when finished, you will be prompted to reboot your computer. <em>Do it:</em> AHCI mode is enabled in Windows 10.</p><p>Note that some computers do not have the option of changing the mode to AHCI in their BIOS. In this case, the problem can sometimes be solved by updating (reflashing) the BIOS version or changing the mode in the OS itself, as described at the beginning of the article.</p><p> </p><div class=


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