This parameter disables the complete ACPI subsystem on your computer. This may be useful if your computer cannot handle ACPI at all or if you think ACPI in your computer causes trouble.
Always enable ACPI even if your computer has an old BIOS dated before the year 2000. This parameter also enables ACPI if it is set in addition to acpi=off.
Do not use ACPI for IRQ routing.
Run only enough ACPI to enable hyper-threading.
Be less tolerant of platforms that are not strictly ACPI specification compliant.
Disable PCI IRQ routing of the new ACPI system.