Transition between SATA Control Modes: from IDE to AHCI


Today my desktop computer has a 1 Tb (almost full) HDD with Sata Control Mode configured as IDE in BIOS. It has Windows 7 Ultimate x64 on it.

I just ordered a new 2 Tb HDD (as the 1 Tb one is running out of space) and plan to do the replacement process as follows:

1.Disconect the 1 Tb HDD;
2.Connect the 2 Tb HDD;
3.Change Sata Control Mode to AHCI in BIOS;
4.Install Windows 10 Pro on the 2 Tb HDD;
5.Connect the 1 Tb HDD as a secondary (non boot) drive, in order to copy my personal data to the new 2 Tb one;

My questions are:

A) Is my plan correct?
B) The data on the the old 1 Tb one will be readable/acessible/not corrupted, considering that it was as previsouly being used with SATA Control Mode configured as IDE in BIOS?
C) If yes/Ok, can I leave it there permanently to be used as a D (secondary) drive? The new Control Mode setting (AHCI) will negativelly affect it?
D) If I need to boot its Windows 7 OS (to check some configuration to configure something on the new HDD), can I temporarily change the control mode to IDE to boot with it (and it will not corrupt the Windows 10 install on the new 2 Tb HDD)?
5 answers Last reply Best Answer
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  1. Best answer
    A) Yes
    B) naw it will work fine. The ahci/IDE problem only applies to boot drives
    C) sure you can leave it in there - but it its gonna be clogged with your old OS data.
    D) that should work just fine. You could alternatively just switch the 1TB to AHCI and call it a day. Its just a simple registry switch.

    Boot your IDE drive in IDE mode.
    Open the Registry editor.
    Navigate to the following key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci
    Change the Start DWORD value from 3 to 0
    Shut down PC
    Go into BIOS
    Change SATA to AHCI

    And tada - AHCI for everything!
  2. No need for all that it is one registry switch to prep for AHCI.

    set the registry, power down, power up, enter bios and set ahci mode, save and exit, boot into windows.

    Now you don't even need to reinstall everything, get some free data migration software usually from the drive vendor, WD or seagate. copy from 1TB to 2TB.

    Then remove the 1TB from sata0 and boot the 2TB in sata0 to make sure all is working, everything there and working well then you can readd the 1TB to sata1, and clean it off to make more storage.
  3. Thank you very much to both of you! I am planning to do a clean Win10 installation instead of cloining the 1Tb drive because it's time to retire Win7 ;) After the 2 Tb is working 100% and everything is installed, I will wipe the Win7 installation from the old one to gain its full space again :-)
  4. Whoops missed the changing OS, still set the windows 7 to AHCI mode with the registry tweak. then unplug the 1TB and install windows 10 on the 2TB in sata socket0, then readd the 1TB in sata1.

    If you need/want to go back to windows 7 change the boot priority in the bios from 2tb to 1TB. to make the data copy easier you would want to put any files to transfer into the c:/users/public folders to avoid permission troubles.
  5. I see. Thanks :)
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