Installing Win7 on a HDD setup for IDE mode in AHCI mode

Discussion in 'Windows 7' started by videobruce, Oct 8, 2013.

  1. videobruce

    videobruce MDL Junior Member

    Feb 16, 2013
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    I'm not sure where to put this, but here it is.

    Using a already formatted & partitioned HDD from a older non GPT ready (if you will) MB, I want to install Win7 64 bit using AHCI. The current O/S on that active partition is XP which I want to replace.
    The other partitions (two) have data on them that I don't want to loose. (I do have it backed up).

    What happens to the drive when I install Win7 in AHCI mode to the other non active partitions?
     
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  2. videobruce

    videobruce MDL Junior Member

    Feb 16, 2013
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    A 2nd question; with a SSD drive that I have installed Win7 on (fresh install), for kicks & giggles, I switched back to IDE mode and booted back into Windows. To mu partial surprise, there was no difference unlike the other way around where you get greeted with a BSOD.

    With that SSD, if I leave the SATA mode to IDE, what is the disadvantage?
     
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  3. lnstevens1976

    lnstevens1976 MDL Junior Member

    Oct 16, 2012
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    I'll start with this one. Windows 7 will install to any partition you choose, and will install in MBR mode onto this drive.

    If you want to retain XP I'm not sure on that. But when you choose the partition to install to you can choose to format it or not, and not affect the other partitions. Also, it will automatically update the MBR on the first partition for boot purposes.
     
  4. lnstevens1976

    lnstevens1976 MDL Junior Member

    Oct 16, 2012
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    AHCI offers a speed benefit, or at least it used to. The difference is if the board supports IDE then IDE drivers get loaded automatically by Windows 7, unlike AHCI which isn't enabled unless the board has it in use. You can switch from IDE to AHCI or back, but to go from IDE to AHCI on a system that has used AHCI requires registry edits.
     
  5. videobruce

    videobruce MDL Junior Member

    Feb 16, 2013
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    I wasn't planning on leaving it to IDE, I was just wondering where I would see a difference since I wasn't sure it would work going from AHCI to IDE. How about GPT vs MBR when Windows is installed? Wouldn't that affect the other non active partitions?

    Lastly, how about "compatibility mode. Why would I want to turn it off?
     
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  6. Techiekid

    Techiekid MDL Member

    Nov 3, 2009
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    It also depends on the make of the motherboard/bios sometimes. Newer boards seem to deal with the IDE/AHCI/RAID switch better, but drivers are very important. I believe GPT drives don't play nice with win xp 32bit OS. Also some large drives like 3TB plus have to be installed as GPT/AHCI on some systems. The issues you encounter may certainly vary with the type of motherboard used. Nothing wrong with AHCI if all your drives are SATA. I just prefer IDE for when I have to plug in the occasional ide drives. Saves me headaches.