I've just installed a new Samsung 830 256GB SSD and have configured BootCamp with Lion and Windows 7.

Under Lion, I have installed Trim Enabler.

Under Windows 7 I have installed the Samsung (Wizard) software that came with the SSD. In this software I've applied all of the recommended optimisations under 'OS Optimisations', however, the Samsung wizard software is informing me that AHCI is not enabled at present and for best performance, this should be enabled.

I'm not sure a) what implications there are if it's left disabled (will it affect the lifespan of the SSD or is it purely a speed thing?) and b) if there is a way under BootCamp for an Early 2011 MacBook Pro to have AHCI enabled?

I was also concerned that if AHCI is not enabled, perhaps TRIM won't be enabled either? However, I did run a tool which I found online that said that TRIM was enabled on this Windows 7 install (despite AHCI not being enabled).

This is my first SSD drive so am not very familiar with the technology, terminology and best practices etc.

5 Answers 5


You can't. Apple has implemented a Compatibility Support Module (CSM) into the Mac firmware that emulates the PC BIOS specification. Since the Mac firmware is not 100% UEFI compliant, that CSM is the only way Windows can boot on a Mac.

Unfortunately, the ACPI tables in that CSM are just the bare minimum necessary to allow Windows to boot and nothing more. You lose several features when using it:

  • No graphics switching (always uses the discrete card).
  • No AHCI support (SATA devices are in IDE compatibility mode)
    • No support for TRIM
    • No support for Native Command Queuing (NCQ).
  • No support for advanced power management features (only basic S1, S3, and S4 states are supported).

Basically Windows sees your SSD as just a really fast IDE hard drive. This will not affect the SSD in terms of lifespan. It may, however, make the SSD a little slower over time than it would otherwise be when running Windows.

NOTE: Some people have reported that they have been able to install Windows 7 in UEFI mode on a Mac, which would enable all those missing features. However, it cannot be done on your model. I've tried. With sufficient hacking you can get it up and running, but it's plagued with audio and video issues.

  • Windows actually needs to be installed in EFI mode on the latest MBPs, which is a first (and perhaps the new MacBook, but I'm uncertain). Jun 27, 2015 at 23:04

You can sacrifice sound or sleep mode and use the AHCI (it is extremely fast), but there isnt way to make it fully functional so far. So now I am using bootcamp and IDE.

Problem is with the emulation of the BIOS, its too old.


Uninstall TrimEnabler, windows does have it automatically, and when it does not work in the Windows partition, it does not work at all. It is still not sure which SSD Controllers are not working well with trim enabled. Marvell is not having any problems; but the Garbage Collection nowadays is so good that Trim does not contribute. Make sure that the SSD has enough free space, say 20-40GB.


For those who have installed any Windows version (7/8/10) using the Legacy BIOS (not EFI) on an iMac or Macbook, I used this method to enable AHCI on both a 2011 iMac and a Macbook Pro and it worked perfectly:

  1. Backup all your data.
  2. Download this AHCI enabler package (contains BOOTICEx64.exe and patchedcode.bin)
  3. Run BOOTICEx64.exe as admin.
  4. On the Physical Disk tab, make sure your destination disk is your desired drive.
  5. Click on Process MBR.
  6. Select Windows NT 5x/6x MBR.
  7. Click on Restore MBR.
  8. Select the patchedcode.bin file.
  9. Make sure Keep signature and partition table untouched is marked.
  10. Click on Restore.
  11. Now open Windows Registry Editor.
  12. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStorV and edit Start DWORD to 0.
  13. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStorAVC\StartOverride and edit 0 DWORD to 0. (This value will return back to 3 after you restart the computer later.)
  14. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\storahci and edit Start DWORD to 0.
  15. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\storahci\StartOverride and edit 0 DWORD to 0.
  16. Close Regedit, reboot your system and you are done.

I want to credit this solution mostly to sanke1's Tutorial: Enable SATA AHCI Mode in Windows 7,8,8.1 & 10 and Shawn Brinks' How to Enable AHCI in Windows 8 and Windows 10 after Installation

Good luck!

  • 2
    Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
    – Community Bot
    Oct 7, 2023 at 15:52
  • If someone can edit this to cover the basics of the steps or comment if they know it's wrong, that would help. It's a start of an answer for sure, but needs an edit
    – bmike
    Oct 7, 2023 at 20:27
  • Done! Sorry for that.
    – SiLenCe
    Oct 8, 2023 at 12:03

In windows go to Control Panel\System and Security\System, click on the "windows experience" link and "Re-Run the assessment" this will update info about the drive and enable trim.

  • Macs do not support TRIM in Windows so your solution wouldn't work.
    – Wes Sayeed
    Sep 23, 2014 at 22:02

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