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How OpenCore handles ACPI

Order of operations

Before you begin fiddling with SSDTs, it's a probably a good idea to take a look at how OpenCore handles ACPI tables and patches. In general, OpenCore applies ACPI changes globally to every operating system (unlike Clover) in the following order:

  1. Patch is processed
  2. Delete is processed
  3. Add is processed
  4. Quirks are processed

ACPI patches integrated into OpenCore

OpenCore offers a few integrated patches ("Quirks") to address and fix specific ACPI tables (besides the DSDT.aml). They are located in the ACIPI/Quirks section of the config.plist:

ACPI_quirks

Quirk Affected Table(s) Table Description What it fixes
FadtEnableReset FACP.aml Fixed ACPI Description Table (FADT). Defines various static system information related to configuration and power management. Fixes reboot and shutdown issues. Can also fix the Power Button: if holding it does not invoke the "Restart, Sleep, Cancel, Shutdown" menu, enable this quirk. If this doesn't fix it, try adding SSDT-PMC.aml. Fixes Low Power S0 Idle state. The FACP table characterizes the machine type and determines the power management method. If Low Power S0 Idle = 1, it's an AOAC system. See the About AOAC section for more details.
NormalizeHeaders All Headers Clear ACPI Header fields Removes illegal characters from ACPI Headers. Only required for macOS 10.13.
ResetLogoStatus  BGRT.aml Bootstrap graphics resource table According to the ACPI specs, the Displayed item of the form should be 0. However, some vendors have written non-zero data to the Displayed entry for some reason, which may cause the screen refresh to fail during the boot phase. The patch sets Displayed to 0. Note: Not all machines have this table.
RebaseRegions All Tables Relocates ACPI Memory Regions ACPI forms have memory regions with both dynamically allocated as well as fixed addresses. This quirk turns dynamically allocated addresses into fixed ones which can help with patched DSDTs.
⚠️ Caution: This patch is very dangerous and should not be chosen unless relocating memory regions solves boot crashes!
ResetHwSig FACS.aml Sets Hardware Signature to 0 Hardware Signature is part of the FACS table. It's calculated after the system has started based on the hardware configuration. If this value changes after the machine wakes up from a Hibernate state, the system will not recover correctly. Note: If the system has Hibernation disabled, you do not need to this quirk!
SyncTableIds SLIC.aml Microsoft Software Licensing table Fixes SLIC table causing licensing issues in older Windows versions.

Note

For more info about ACPI Tables in general, please refer to the official ACPI Specs.

Credits