12 Replies Latest reply: Feb 9, 2016 4:22 PM by plato1123
SkyriderUK Level 1 (0 points)



There is a well known mod to the OS X MBR to enable AHCI for Windows 7.


Sadly it does not seem to work for Windows 8. This is partly due to a change in the Windows Registry:




I guess this requires a change to the old mod: anyone know how to do this please?

iMac, Mac OS X (10.6.7)
  • CT Level 6 (17,545 points)
  • SkyriderUK Level 1 (0 points)

    Thanks for the link but I couldn't find anything helpful there.


    However, I have now resolved this:


    In the 'storahci' tree there is a 'startoverride' entry. It is also necessary to change this to 0 after which you apply the old patchedcode in Terminal in OS X.


    However, on reboot I found that almost everything was inop, including my mouse & keyboard. Inspection of 'Device Manager' in Windows showed that one of the USB Root Hubs was disabled:


    I went to Update Driver >Browse my computer>Let me pick>USB Root Hub the restarted the computer.


    All now working in AHCI mode

  • rturner2 Level 1 (0 points)

    Thanks SkyriderUK... this worked for me.


    I was wondering why my Macbook Pro late 2011 was running a bit slow, considering I had installed a Samsung 830 512GB SSD. It was because AHCI was disabled (see below for performance before and after).


    However... I did run into some issues.


    Firstly I want to make the process clearer for others as I had trouble understanding exactly what to do:


    1) Follow the Steps on this page except Step 8: http://www.ithinkdiff.com/how-to-enable-ahci-in-windows-8-after-installation/


    2) Restart and go into the Mac side of your computer


    3) Follow this guide: http://www.adminsehow.com/2012/10/how-to-enable-ahci-support-for-windows-on-an-i mac-macbook-or-etc/


    3a) To copy over the "patchedcode.bin", make sure you boot onto an external USB key or DVD. I used the reinstall Mac OS X DVD that came with my computer.... loaded this but didn't install. Just accessed Terminal using the drop down menus at the top.


    4) When I rebooted into Windows 8 for the first time, my computer wouldn't load. Error screen during startup. Had to reboot.


    4a) One the third boot of Windows 8, it offered to do a "roll back" for me. I did this. Still didn't work ie. couldn't book Windows 8.


    4b) Luckily I had Parallels on the Mac side. I loaded my Bootcamp install of Windows 8 via Parellels on the Mac side. Because I did a roll back, I had to make the necessary registry changes again outlined in http://www.ithinkdiff.com/how-to-enable-ahci-in-windows-8-after-installation/


    5) Then I rebooted back into Windows 8 and it loaded this time for me. Thank goodness. Now AHCI is working!!!


    So how it my system running? Was it worth the effort?


    See image below. Dark blue is running AHCI, light blue is before running AHCI. A big difference!!!



    Hope this post helps others.

  • Julianbl Level 1 (0 points)


    What about sleep? does it work?

    I could activate AHCI on my MBP 13 late 2011 but whenever it cames back from sleep, it crashes. Found on forums that this happens to almost everyone.





  • Bladedmink Level 1 (0 points)

    Have provided a step by step guide on turning on AHCI support on a Mid 2010 Macbook Pro model



  • CT Level 6 (17,545 points)
  • 2tired2care Level 1 (0 points)

    I take it Bladedmink's most recent post will work about the same for Windows 7 Home Premium 64-bit? Been having a lot of issues getting Windows 7 and my Samsung 840 Evo with Samsung's software to enable AHCI and getting it to work properly.

  • camuman Level 1 (0 points)

    i dont think so. i just looked for the reg keys and couldnt find the same folders he referenced.  PLEASE, if you are willing, find out how to do it that easily with windows 7!

  • Gunni_F Level 1 (0 points)

    I'm having the very same problem.


    Using patchcode.bin to batch the MBR I was able to ENABLE AHCI for Windows on my iMac 2011.
    But now after sleep Windows 8 starts, crashes, reboots and continues at the point where it should have.


    Running windows7 show a similar behavior: I'm not sure whether it happens after sleep or after shutdown but Windows boots into system repair instead of the os from time to time. A simple hard reboot will fix it.


    How can we fix this issue?

  • CT Level 6 (17,545 points)
  • Gunni_F Level 1 (0 points)

    Your answer is sarcastic and doesn't help. Was it really necessary to post such a useless answer?

  • plato1123 Level 1 (0 points)

    Is it possible to patch the MBR without OSX installed?  I have a macbook pro with only windows 8 and do not have any OSX installation or disk.  Someone said something about doing it from a linux terminal?  Maybe I could use a boot cd like hirems to patch it?  Thanks for your help,