AHCI, abbreviation for advanced host controller interface, is the native work mode for SATA drives. AHCI has two main benefits: support for hot pluggable SATA drives (mimicking USB drives' behavior) and NCQ, or native command queuing. It has been present in the Linux kernel since version 2.6.19 and will be loaded automatically in current Arch kernel.
Configure from BIOS
If your BIOS set SATA as legacy/parallel ATA, you can access BIOS setting depends on the motherboard; usually,
Del is used to display the menu.
Once the BIOS options are available, search for parameters resembling:
Enable SATA as: IDE/AHCI
SATA: PATA Emulation/Native/Enhanced
Native, save the settings and exit the BIOS. Consult the motherboard's manual if it's not clear which of the modes is AHCI, since the naming can vary.
After altering and saving the BIOS settings, Linux should load the AHCI driver on the next boot.
dmesg's output should confirm this:
SCSI subsystem initialized libata version 3.00 loaded. ahci 0000:00:1f.2: version 3.0 ahci 0000:00:1f.2: PCI INT B -> GSI 19 (level, low) -> IRQ 19 ahci 0000:00:1f.2: irq 764 for MSI/MSI-X ahci 0000:00:1f.2: AHCI 0001.0200 32 slots 6 ports 3 Gbps 0x3f impl SATA mode ahci 0000:00:1f.2: flags: 64bit ncq sntf stag pm led clo pmp pio slum part ems ahci 0000:00:1f.2: setting latency timer to 64 scsi0 : ahci scsi1 : ahci scsi2 : ahci scsi3 : ahci scsi4 : ahci scsi5 : ahci
and for NCQ:
ata2.00: 625142448 sectors, multi 16: LBA48 NCQ (depth 31/32)
It is possible that the AHCI module is not loaded automatically, if SATA configuration is switched from IDE to AHCI after installing Arch. In such case, an error message appear at early boot indicating that the root partition was not found.
If that happens, the
failsafe boot option should still works fine.
Once started in failsafe mode, you have to run mkinitcpio to re-generate a correct initramfs images.