Certain settings choices can cripple system performance severely while others are capable of giving a small boost which is always a good thing to have. Thankfully there are those that will test settings until their faces turn blue.
Benchmark Reviews tries out ACHI and IDE settings when running a number of SATA Solid State Drives. The conclusion is quite clear:
Most computer motherboards offers hardware enthusiasts the option to adjust the SATA interface settings in their BIOS between AHCI and IDE mode. Traditionally, IDE is the time-tested standard for desktop hard drive products. The IDE interface offers basic control over the storage device, but does not include enterprise-level features. Advanced Host Controller Interface (AHCI) on the other hand, was created as a means to deliver additional storage support for server backplanes and high-end performance desktop computers. While there are really very few differences between these two disk IO settings, AHCI includes hot-swap drive support and Native Command Queuing that is not available in IDE mode.
I won’t play spoiler on their article but it’s something to keep in mind when you make the move to a SSD setup.