Difference between revisions of "AHCI"

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Advanced Host Controller Interface ([http://en.wikipedia.org/wiki/AHCI AHCI]) is the '''native''' work mode for SATA drives. It's been in the Linux kernel since version 2.6.19. Enabling AHCI has two main benefits: support for hot pluggable SATA drives (just like USB) and Native Command Queuing ([http://en.wikipedia.org/wiki/NCQ NCQ]).
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[[Category:Storage]]
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[[es:AHCI]]
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[[ja:AHCI]]
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[[zh-hans:AHCI]]
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[[Wikipedia:AHCI|AHCI]] (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 [[Wikipedia:Native Command Queuing|Native Command Queuing]] (NCQ). It has been present in the Linux kernel since version 2.6.19 and will be loaded automatically in current Arch kernel.  
  
SATA drives are usually configured as '''legacy''' Parallel ATA by the BIOS and the OS. Follow these two steps to enable AHCI:
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== Configure from BIOS ==
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If your BIOS set SATA as legacy/parallel ATA, you can access BIOS setting depends on the motherboard; usually, {{ic|Del}} is used to display the menu.
  
==== Add the AHCI module to the kernel image ====
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Once the BIOS options are available, search for parameters resembling:
We do this by editing /etc/mkinitcpio.conf and adding ahci to the MODULES array:
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Enable SATA as: IDE/AHCI
 
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or:
<code>
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SATA: PATA Emulation/Native/Enhanced
MODULES="ahci"
 
</code>
 
 
 
Then we rebuild the kernel image, so that it includes our module:
 
 
 
<code>
 
mkinitcpio -p kernel26
 
</code>
 
  
==== Configure from BIOS ====
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Choose {{Ic|AHCI}} or {{Ic|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.
This depends from one motherboard to another. Enter the BIOS and search for something like:
 
  
<code>Enable SATA as: IDE/AHCI</code>
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After altering and saving the BIOS settings, Linux should load the AHCI driver on the next boot. {{Ic|dmesg}}'s output should confirm this:
 
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<pre>
or:
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SCSI subsystem initialized
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libata version 3.00 loaded.
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ahci 0000:00:1f.2: version 3.0
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ahci 0000:00:1f.2: PCI INT B -> GSI 19 (level, low) -> IRQ 19
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ahci 0000:00:1f.2: irq 764 for MSI/MSI-X
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ahci 0000:00:1f.2: AHCI 0001.0200 32 slots 6 ports 3 Gbps 0x3f impl SATA mode
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ahci 0000:00:1f.2: flags: 64bit ncq sntf stag pm led clo pmp pio slum part ems
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ahci 0000:00:1f.2: setting latency timer to 64
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scsi0 : ahci
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scsi1 : ahci
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scsi2 : ahci
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scsi3 : ahci
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scsi4 : ahci
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scsi5 : ahci
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</pre>
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and for NCQ:
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ata2.00: 625142448 sectors, multi 16: LBA48 NCQ (depth 31/32)
  
<code>SATA: PATA Emulation/Native/Enhanced</code>
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== Troubleshooting ==
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It is possible that the AHCI module is not loaded automatically if SATA configuration is switched from IDE to AHCI after installing Arch.
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In such case, an error message will appear at early boot indicating that the root partition was not found.
  
Choose AHCI or Native, save your settings and exit the BIOS. Consult your motherboard manual if you don't know which of the modes is AHCI since the naming can vary.
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If that happens, the {{Ic|failsafe}} boot option should still work fine.
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Once started in failsafe mode, you have to run [[mkinitcpio]] to re-generate initramfs images.

Latest revision as of 10:22, 18 May 2019

AHCI (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 Native Command Queuing (NCQ). 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

or:

SATA: PATA Emulation/Native/Enhanced

Choose AHCI or 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)

Troubleshooting

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 will appear at early boot indicating that the root partition was not found.

If that happens, the failsafe boot option should still work fine. Once started in failsafe mode, you have to run mkinitcpio to re-generate initramfs images.