Any way to force AHCI mode on ICH8?

Morgan Wesström freebsd-questions at
Thu Sep 9 13:51:39 UTC 2010

On 2010-09-09 13:04, Ivan Voras wrote:
> On 09/09/10 02:10, Morgan Wesström wrote:
>> I run FreeBSD 8.1 on an old Asus P5B-VM motherboard with ICH8. Its AMI
>> BIOS lacks an option to enable AHCI mode. Intel's datasheet for the ICH8
>> family specifies that this feature exists on the ICH8, and the option is
>> available in the BIOS for the identical (apart from form factor) P5B
>> motherboard.
>> I've contacted Asus support for an updated BIOS but I don't have much
>> hope I will ever see one. Would it be possible to patch the FreeBSD
>> kernel to enable AHCI mode somehow during boot?
> You mean except adding:
> ahci_load="YES"
> to /boot/loader.conf ?

Yes, I meant if there was a way to programmatically switch the ICH8 into
AHCI mode before loading ahci(4). The BIOS on this motherboard only
provides a "legacy" and an "enhanced" option for the SATA controller.
Neither option turns on AHCI mode so ata(4) attaches to the controller.
There's also a JMicron controller, providing an eSATA connector, on this
motherboard. It is AHCI compatible and ahci(4) attaches correctly to it.
It would've been nice to be able to use NCQ and hotplug on the other
SATA connectors too since the ICH8 has those features.


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