AHCI vs IDE
IDE stands for Integrated Drive Electronics. This has been the standard interface that is used for storage media like hard drives and optical drives for a considerable length of time. Though there were some hurdles at the beginning, the standard was eventually perfected and different drives from different manufacturers can attach to most motherboards. IDE was superseded by SATA as it introduced a lot of advantages. AHCI (Advanced Host Controller Interface) is an application programming interface that defines one mode of operation for SATA. AHCI does not affect the speed at which SATA drives operate but it exposes the advanced features that are available with SATA.
To maintain backwards compatibility with older hardware, most SATA controllers provide you with the choice of which operation mode you want to use. Operation modes include AHCI and IDE, often referred to as legacy IDE or native IDE, among others so that you have freedom. Choosing IDE as your mode of operation is just like having a good old reliable IDE drive but without the benefits of AHCI.
AHCI allows users to utilize advanced features that are available to SATA. The first feature is Native Command Queuing or NCQ. Without NCQ, each request is served sequentially without any optimization. NCQ analyzes the requests and rearranges them so that requested data locations that are physically closer to each other are grouped together so that they can be accessed in one pass and the time needed is minimized. AHCI also enables hot-plugging or the ability to attach or remove hard drives from a system that is running similar to a removable drive. This is not possible with IDE drives as they are configured during boot time.
The choice, of whether you would be using AHCI or IDE, is done prior to installing the operating system on the computer as switching from one to the other after would often lead to the system not working properly if at all. Most operating systems now have patches to address this problem but specific steps needs to be followed prior to switching.
Summary:
1.IDE is an old interface standard used for storage devices while AHCI is an application programming interface for the newer SATA interface.
2.Most SATA controllers allow you to choose between AHCI and IDE among other operation modes.
3.AHCI has advanced features like NCQ and hot plugging that is not available with IDE.
4.Switching from IDE to AHCI or vice versa after the operating system is installed can lead to problems.