In the world of host controllers and controller interfaces to control and give tasks to the host controllers many terms or names of devices and interfaces can be found.
The most common terms one can come across are AHCI and ATA. One being controller interface and the other being the host controller. It has often been a task to be able to differentiate between them.
AHCI vs ATA
The main difference between AHCI and ATA is that ATA is the host controller and AHCI is the controller interface that was designed for SATA or Serial ATA which is an updated version of ATA.
AHCI or Advanced Host Controller Interface as the name suggests is a controller interface that is used for specifying the tasks or actions of other host controllers they are designed for. It is defined by Intel as a necessary technical standard for defining the operations.
ATA or Advanced Technology Attachment is the host controller that defines the passage of information between storage and a host. They also connect storage devices. ATA is usually connected to a motherboard but can be found to be connected to two hard drive devices.
Comparison Table between AHCI and ATA
| Parameters of Comparison | AHCI | ATA |
| Abbreviation for | Advanced Host Controller Interface | Advanced Technology Attachment |
| Meaning | It is a controller interface | Connects storage device |
| Version | Relatively new | It is an old version |
| Applications | It specifies the actions of the host controllers like SATA | The passing of information between storage and the host. |
| Advantage | It has updated features like hot-plugging and NCQ | It is compatible with older versions of devices |
| Implementing | Hard to implement | Relatively easier to implement |
What is AHCI?
AHCI or Advanced Host Controller Interface is the controller interface that specifies the actions by the host controllers like SATA. They have two added features of NCQ and hot-plugging.
NCQ or Native Command Queuing allows the controllers to change the order for receiving all the required output and data with a minimum number of spins. Hot-plugging is the ability to add/remove hard-drives from the system without having to reboot the entire system.
So, it treats hard drives as removable memory cards. Since they are relatively new and an updated version, they are not compatible with the older versions of ATA or PATA. So, if ATA is already connected to your operating system, to change it you may have to install a fresh operating system and the correct AHCI.
It is used by designers and hardware developers to give standard methods for detection and configuration of the SATA adapter. They are harder to implement as they are compatible with only SATA.
What is ATA?
ATA is an Advanced Technology Attachment that passes information between storage and the host. It is a host controller and can be said to be an interface between the storage and the host as it connects the right storage device. The first-ever ATA was made in 1986
There are two types of ATA: PATA and SATA. SATA is the later version of ATA and is compatible with AHCI up to a limit since it was designed for SATA or Serial ATA. Parallel ATA or PATA and ATA are acronyms as they are usually used to refer to one another.
Though AHCI was made for SATA, SATA can also operate on IDE. There is also much hardware that supports SATA without AHCI. ATA has a reliable speed and is also one of the most common and cheapest interfaces available.
They are backward compatible i.e., the newer versions of ATA can be used with the old ATA interface. Usually, ATA is connected to a motherboard from one end and a hard drive at the other end. They can also be connected to two devices where one is called a slave and the other a master.
Main Differences Between AHCI and ATA
- AHCI stands for Advanced Host Controller Interface whereas ATA stands for Advanced Technology Attachment.
- AHCI is just a controller interface that runs with the later version of ATA called SATA. ATA is the one that connects storage devices.
- Since AHCI was designed for Serial ATA, it is relatively new as compared to ATA. It is because ATA is old that AHCI is not compatible with it.
- ATA is used for connecting a storage device with a host as it is a host controller. Since AHCI is a controller interface, it specifies the actions of host controllers.
- The advantages of AHCI over ATA is that they have two added features that are not there in ATA, which are NCQ and hot-plugging. The hard drive of AHCI is treated like removable memory chips. Whereas, ATA is reverse compatible. The newer versions are compatible with the old ATA, unlike AHCI.
- If one has an operating system it is easy to install or implement ATA. But once ATA is installed, it would be difficult to implement AHCI as it requires installing a fresh browser and getting AHCI from the correct software.
Conclusion
A host controller interface is an interface that allows communication between the host controller device and host controller software. A host controller on the other hand is a software that is installed to allow the flow of information between two devices.
AHCI also called as Advanced Host Controller Interface, is a host controller interface that was designed for Serial ATA that is an updated version of ATA. AHCI is used for specifying and assigning tasks to the host controller and cannot be used without a host controller it is compatible with.
ATA also called as Advanced Technology Attachment is a host controller that was first designed in 1986. There are two types: Parallel ATA (PATA) that was initially called as ATA but on the introduction of Serial ATA( SATA), it was renamed to PATA. All versions of ATA are compatible with one another as it has reverse compatibility.
The difference between ATA and AHCI is that, since ATA is not compatible with AHCI it has to be used with other host controllers. But the later version of ATA i.e., SATA is compatible and is easy to implement. AHCI can be difficult to implement in an operating system.
References
- https://books.google.com/books?hl=en&lr=&id=8O-sBAAAQBAJ&oi=fnd&pg=PP1&dq=AHCI+vs+ATA&ots=izUFlPiqcj&sig=FGc9UNwYJ7Rv2Y9FZbrKKqh0Mm8
- http://www.barrelfish.org/publications/stocker-nevill-gerber-dslab-disk.pdf