Enabling AHCI - is modifying the registry enough?

[Popculturereference]

Hello, first time poster here, so excuse any potential breaches of etiquette.

I just could not for the life of me find anything via Google in regards to specifics about enabling AHCI mode. I have recently purchased an SSD, except I installed Windows 8.1 on it in IDE mode. I have found out about AHCI later, successfully enabled it in the registry and then in BIOS.

My SSD - Samsung 840 Evo 250 GB - still underperforms, though. It has never reached anywhere near 90k or even 80k out of its maximum 97k of random read. I have browsed questions (mostly here, actually) regarding potential SSD slowdowns, tried everything and it still is yet to exceed 70k after what I am guessing is about a dozen tests by now.

The question here, though, is whether it's okay to enable AHCI in the registry & BIOS after the OS installation was completed in IDE mode. Am I better off reinstalling it in AHCI proper, or does that make no difference?

 

[Z1NONLY]

For 7, it doesn't make a difference. (Proper or after the fact)

I went AHCI after-the-fact. All it did was prompt the OS to re-introduce itself to the drive as if it was their first encounter. Then it chooses how to handle it based on what it finds.

If you set your MB to AHCI and your OS isn't crashing on start-up. It worked.