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Forgot to enable AHCI mode after installing SSD!

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#1 Marth_01


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  • Local time:08:25 PM

Posted 29 April 2013 - 10:11 AM

So, I bought an SSD, plugged it into my SATA 3 port on my motherboard, installed all my programs, and have been using it for a couple months. The speed is very fast and a very noticeable difference from my old western digital black 7200rpm drive. I recently did a speed test using CrystalMark and ATTO, and noticed my sequential read/write is only about 300/240 MB/s, while the SSD says it goes up to 530/240 MB/s read/write.

1. Is this because I forgot to enable AHCI on my mobo?
2. If I want to change to AHCI, will it clear the disk?
3. What's the best way of switching if it clears the disk - Norton Ghost?


SSD - Samsung 840 - 250gb
MOBO - Gigabyte GA-P55A-UD4P

Thank you for your time!

EDIT: Is this the solution for switching modes after Windows 7 has been installed?


  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\pciide

When the system is in IDE interface mode, the respective start values are:

  • msahci's START value is "3"
  • pciide's START value is "0"

When the system is in AHCI interface mode, the respective start values are:

  • msahci's START value is "0"
  • pciide's START value is "3"

2. Switch BIOS from to version you want to use.

Is this correct?  Are there any other troubles I may run into?  Also, for verification I checked and my values are the IDE ones.

Edited by Marth_01, 29 April 2013 - 10:23 AM.

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