Advantages of AHCI | Disadvantages of AHCI

This page covers advantages and disadvantages of AHCI (Advanced Host Controller Interface). It mentions benefits or advantages of AHCI and drawbacks or disadvantages of AHCI.

What is AHCI ?

AHCI offers advanced features to serial ATA standard. AHCI is PCI class device which allows data movement between system memory and SATA devices. AHCI host devices support about 1 to 32 ports. AHCI host devices are known as HBA (Host Bus Adapters). HBA supports ATA and ATAPI devices in addition to PIO and DMA protocols. It is designed for HDD with spinning disk technology.

AHCI specification was developed by AHCI contributor group comprised of various companies which include software, hardware, OEM vendors and led by Intel. Latest version of AHCI specification is 1.3.1. AHCI operating mode is found in BIOS settings of PCs.

AHCI interface

AHCI encompasses PCI device which contains base address register (BAR) in order to implement native SATA features. It has only one command queue. It can only send 32 commands per queue. AHCI is supported by Windows Vista and latest versions of windows, linux, OpenBSD, FreeBSD, NetBSD, Solaris 10, OS Z and eComStation.

Following are the features of AHCI interface as defined in its specification version 1.3.1.
• Supports 32 ports
• 64 bit addressing
• Elimination of master/slave handling
• Large LBA support
• Hot Plug
• Power Management
• HW assisted native command queuing
• Staggered spin up
• Cold device presence detect
• Serial ATA superset registers
• Activity LED generation
• Port Multiplier

Benefits or advantages of AHCI

Following are the benefits or advantages of AHCI:
➨AHCI accesses native command queuing (NCQ) of SATA interface. Hence it improves compatibility and performance of devices.
➨Due to hot plugging feature, devices can be added or removed to/from computer system while it is running.
➨It offers improved communication speed beween host and drive. Hence fast data exchange is possible.
➨It adds advanced management features to SATA drives.

Drawbacks or disadvantages of AHCI

Following are the drawbacks or disadvantages of AHCI:
➨The AHCI commands utilize high number of CPU cycles.
➨It is not always compatible.
➨It supports less queue depth compare to NVMe. AHCI supports 1 command queue with 32 commands per queue. NVMe supports 64 queues with 64K commands per queue.
➨It supports single interrupt and does not support interrupt steering. NVMe supports 2K MSI-X interrupts.
➨It requires synchronization and lock to issue command.
➨AHCI is a older technology. It does not support clusters.
➨AHCI works only on Intel chipsets.

Refer advantages and disadvantages of NVMe interface used for SSD (Solid State Drive).

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