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    Windows wont boot after succssesful BIOS flash? / How to switch to AHCI mode, if windows already installed on IDE mode?

    Discussion in 'Acer' started by BoxCat, Jan 21, 2011.

  1. BoxCat

    BoxCat Notebook Enthusiast

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    Hello, here is a lil tutorial that might will help somebody and saves from reinstalling windows and losing all settings =)

    Warning: tutorial applies only for Windows Vista and Windows 7! I dont know how to do this on XP.

    So, if you flashed your machine with newer version of BIOS and after restart windows, it crashes on loading screen and shows blue screen then reloads in to help menu, its might just because new BIOS version has default SATA Hard Drive settings set to AHCI mode, and its used to be on IDE mode.
    Ur windows probably was installed on IDE mode, so whole windows driver configuration is to IDE mode and it wont recognize new AHCI mode settings.
    So simply go to BIOS settings (by pressing F2 or dedicated button till it loads) and change it back to IDE, save settings and restart. Windows now should boot normally.

    Still, now u might wanna make ur machine work on AHCI mode cause:

    What is AHCI and why its better then IDE?

    Most current notebook nowadays allow user to set hard disk interface either AHCI (advance) or IDE (legacy). There are several reason why we should use AHCI instead of IDE. One of AHCI advantage is NCQ (Hot swappable seem not so relevan to notebook aight).
    The Advanced Host Controller Interface (AHCI) is a hardware mechanism that allows software to communicate with Serial ATA (SATA) devices such as host bus adapters which are designed to offer features not offered by Parallel ATA (PATA) controllers besides higher speeds, such as hot-plugging and native command queuing.

    AHCI stands for Advanced Host Controller Interface. One of the main reasons for switching to AHCI-mode is to take advantage of the NCQ-Feature of your SATA harddrive. NCQ (Native Command Queuing) allows ATA drives to accept more than one command at a time and dynamically reorder the commands for maximum efficiency. NCQ, when used in conjunction with a hard drive that supports NCQ, can increase storage performance on random workloads.

    [​IMG]

    Native Command Queuing (NCQ) is a technology designed to increase performance of SATA hard disks under certain situations by allowing the individual hard disk to internally optimize the order in which received read and write commands are executed. This can reduce the amount of unnecessary going back-and-forth on the drive’s heads, resulting in increased performance (and slightly decreased wear of the drive) for workloads where multiple simultaneous read/write requests are outstanding, most often occurring in server-type applications. However, the current technology actually slows down HD access in certain applications, like games and sequential reads & writes, because of the added latency induced by NCQ logic.

    AHCI is fully supported in Microsoft Windows Vista and Windows 7 and the Linux operating system from kernel 2.6.19. Older operating systems like Windows XP require drivers written by the host bus adapter vendor in order to support AHCI. Windows XP requires the installation of a vendor-specific driver even if AHCI is present on the host bus adapter because Windows XP was released before Serial ATA was invented.

    So, how to enable AHCI if you already install Windows Vista using IDE interface?

    Solution:

    1. Exit all Windows-based programs.
    2. Click Start, type regedit in the Start Search box, and then press ENTER.
    3. If you receive the User Account Control dialog box, click Continue.
    4. Locate and then click the following registry subkey:
    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
    5. In the right pane, right-click on "Start" key , and then click Modify.
    6. In the Value data box, type 0, and then click OK.
    7. On the File menu, click Exit to close Registry Editor

    Reboot your notebook, enter bios (F2, del etc), change your hard disk interface to AHCI. Save settings, restart, now your notebook should all boot fine. After it logs in to windows, u will get warning about new hardware, it will install bunch of new devices, then it will ask u to restart. Restart it, and u ready to go, u should notice faster boot up time and better performance.

    Hope this helps to somebody, cheers ;)
     
    BoxCat, Jan 21, 2011
    #1