Previous 1 2 Next 16 Replies Latest reply: Aug 5, 2011 2:42 PM by dmdimon
msuh110 Level 1 (0 points)
i know people have enabled AHCI in MB Pro's. there's a bunch of information regarding that laptop. i've tried to follow those directions but AHCI just won't turn on. i'm wondering if the PCI IDE Controller just doesn't support AHCI or if i'm doing something wrong.

does anyone have any information regarding this matter?

thanks in advance.

MacBook Air 11" 1.6Ghz 4GB Ram 128GB SSD, Mac OS X (10.6.4), Windows 7 Ultimate 64
  • Craig Brady Level 4 (1,790 points)
    Which features of AHCI are you wanting to take advantage of? It only looks like command queueing would give you a possible performance advantage on the MBA with SSD.
  • SergeF Level 1 (25 points)
    The most important one is TRIM command support, wich is required for SSD! TRIM is only available in AHCI mode. However, Apple disabled AHCI when booting from bootcamp partition (and re-enable it when booting from Macintosh HD).

    *Apple, we need AHCI for bootcamp!*
  • ge2kaslt Level 1 (0 points)
    Looking for AHCI drivers for windows 7 all evening but i looks there is no solution for this...
  • dm_dimon Level 1 (0 points)

    try this:


    1. In Device Manager, find the Standard Dual Channel PCI IDE Controller.

    2. Choose 'Update Driver Software', 'browse ...', 'let me pick ...'.

    3. Uncheck 'Show compatible hardware'.

    4. Choose 'Standard AHCI 1.0 Serial ATA Controller' in the manufacturer list, and the same for model (should be the only model)


    It may be enough.

    If not - search net for AHCI Enabler program. It have instructions packed and should be started under OS X

    originated from:

    Johnsock with the help of others made a GUI application to run in OSX that modifies the MBR for you in a much simpler and less frightening way several months ago... I spaced out on updating the first post for a long while... direct link to his application is here ... Link to his post is here.

    This is still considered to be BETA and most likely always will be. We are not responsible for any of your data if you or the application destroys BACKUP!

    It works on the INTEL CHIPSETS ONLY (having nvidia or ati graphics cards is ok) Running Leopard, Snow Leopard, or Lion (Tiger unknown) to make the modifications to the MBR
    Currently NTFS only Partitions are supported (can share boot drive with OSX)
    Mac Pro - All Models as of this writing
    MacBook (Pro) - ICH8 (Core /2/ Duo/Solo) thru Mid 2010 Core i5 / i7
    iMac - With Core i5 / i7

  • The hatter Level 9 (60,925 points)

    Background Garbage Collection is more important than TRIM, and any current Sand Force based SSD controller and firmware.

  • dm_dimon Level 1 (0 points)

    just think a bit about:

    what "trim vs idle GC" have to do with topicstarter question?

    who told you that? sellers of SF2xxx-based SSDs?

    what in this context should do owners of Apple SSD?

    do you know that ALL SF2xxx drives, new Intels, new Crucials - e.g. virtually all drives with capable GC just does not work reliably in MBP2011 15-17 due to sata3 instability? So owners of this(and I'm one of them) just HAVE TO use previous generations of SSD with far worse GC or pray?

  • moocowsforever Level 1 (0 points)

    I wish apple would start using UEFI 2.1 so Windows 7 could use AHCI and boot quickly, without BIOS emulation. Do you think apple is likely to consider this with future boot camp? I also don't like how you have to have a hybrid MBR and GPT so you have to be careful how you partition drives and stuff. Seems a waste of hardware.

  • The hatter Level 9 (60,925 points)

    Apple does use Unified EFI 2.x but it is likely closed, proprietary, but they and intel and MS are part of the EFI and UEFI Group. And that was adopted in late 2007. The Mac Pro Early 2008 supports and was the first to use it. But it isn't universal probably across the product lineup.


    UEFI requires GPT and Windows Vista SP1 64-bit and later (as well as Server 2008) but you don't find many PC motherboards with EFI or UEFI - a very few as of now.

  • dmdimon Level 3 (840 points)

    funny thing. It is windows that have problems with EFI/UEFI and GUID GPT support - but you want Apple to do something. Why you not asking Microsoft?

  • moocowsforever Level 1 (0 points)

    I'm asking Apple because of their use of a proprietary EFI and not a unified form, which causes many problems. (Thanks Hatter). I wouldn't expect Microsoft to develop support for proprietary standards as they have a responsibility to cooperate with many manufacturers. I don't think enabling AHCI in the BIOS emulator would be too difficult for Apple either.


    I'm fairly balanced on the Microsoft vs Apple debate, but I can't help always hoping that Apple would use more compatible standards.

  • dmdimon Level 3 (840 points)

    Apple uses a proprietary extensions for perfectly standart, even a bit outdated base EFI. Big difference with proprietary efi. Just for you to know - you can grab (opensorced, standart) UEFI, compile it yourself in MS Visual Studio under windows and Apple's extensions will perfectly load into it at runtime.

    I'd recommend you read this:

    exactly pay attention to this:

    * The GUID Partition Table (GPT) was introduced as part of the Unified Extensible Firmware Interface (UEFI) initiative.

    and than - this:


    Windows XP x64 Edition can use GPT disks for data only.

    The 32-bit version will see only the Protective MBR. The EE partition will not be mounted or otherwise exposed to application software.

    Starting with Windows Server 2003 Service Pack 1, all versions of Windows Server can use GPT partitioned disks for data. Booting is only supported for 64-bit editions on Itanium-based systems.

    Can Windows 7, Windows Vista, and Windows Server 2008 read, write, and boot from GPT disks?

    Yes, all versions can use GPT partitioned disks for data. Booting is only supported for 64-bit editions on UEFI-based systems.


    Last one sounds good, yes? Actually no:

    Windows GPT Required Partitions

    EFI System Partition

    What is the Extensible Firmware Interface System Partition (ESP)?

    The ESP contains the NTLDR, HAL, Boot.txt, and other files… blabla

    Do you really think that NTLDR, HAL, Boot.txt are parts of OS-independent UEFI standart?

    Can there be two ESPs on a single disk?

    Such a configuration should not be created and is not supported in Windows.

    So Apple just can not create special win-specific partition for Windows to load directly - it just does not support it


    Microsoft Reserved Partition

    What disks require an MSR?

    Every GPT disk must contain an MSR. The order of partitions on the disk should be ESP (if any), OEM (if any) and MSR followed by primary data partition(s). It is particularly important that the MSR be created before other primary data partitions.

    Do you really think that Microsoft Reserved Partition is a part of OS-independent GUID GPT standart?


    Q.          Who creates the MSR?

    The MSR must be created when disk-partitioning information is first written to the drive. If the manufacturer partitions the disk, the manufacturer must create the MSR at the same time.

    So for windows to boot directly, Apple should themselves create windows non-standard partition on every mac sold.

    And, furthermore, it (Apple) have to install NTLDR, HAL, Boot.txt and other MS crap on every mac. Paying license fee for that.


    It's not my fantasies - it's open data from Windows Hardware Developer Center > Learn > Devices > Storage Technologies > Windows and GPT FAQ of MS itself.

    And same story you can find about UEFI support on Windows. Non-standard things required here and there.


    Do you know that Linux can boot on macs directly, as it doesn't require some MSR sh*t and such?


    There are a lot of things to blame Apple, but not this one

  • dmdimon Level 3 (840 points)

    SergeF, that doesnt matter if trim will work only on mac partition - if you use mac partition more actively than windows.

    See, on lowest level all SSD NAND space is unified - so when you clean blocks under OS X on HFS+ you actually clean that blocks for any OS and any partition to write on them.

    The only question is - will space, TRIMmed under OS X will be enough for your usual writes under windows - that only tests can say.

  • dmdimon Level 3 (840 points)

    actually there are perfect link with a bit other point of vision (Thanks to Christopher Murphy):

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