Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
that assumes the presence of these devices and their associated resources. These flags are used
independently of the ACPI namespace. The presence of other devices must be described in the ACPI
namespace as specified in Section 6, “Configuration.” These flags pertain only to IA-PC platforms.
On other system architectures, the entire field should be set to 0.
Table 5-36 Fixed ACPI Description Table Boot IA-PC Boot Architecture Flags
IAPC_BOOT_ARCH
Bit
length
Bit
offset
Description
LEGACY_DEVICES 1 0 If set, indicates that the motherboard supports user-visible
devices on the LPC or ISA bus. User-visible devices are devices
that have end-user accessible connectors (for example, LPT
port), or devices for which the OS must load a device driver so
that an end-user application can use a device. If clear, the OS
may assume there are no such devices and that all devices in the
system can be detected exclusively via industry standard device
enumeration mechanisms (including the ACPI namespace).
8042 1 1 If set, indicates that the motherboard contains support for a port
60 and 64 based keyboard controller, usually implemented as an
8042 or equivalent micro-controller.
VGA Not Present 1 2 If set, indicates to OSPM that it must not blindly probe the VGA
hardware (that responds to MMIO addresses A0000h-BFFFFh
and IO ports 3B0h-3BBh and 3C0h-3DFh) that may cause
machine check on this system. If clear, indicates to OSPM that it
is safe to probe the VGA hardware.
MSI Not Supported 1 3 If set, indicates to OSPM that it must not enable Message
Signaled Interrupts (MSI) on this platform.
PCIe ASPM Controls 1 4 If set, indicates to OSPM that it must not enable OSPM ASPM
control on this platform.
CMOS RTC Not
Present
1 5 If set, indicates that the CMOS RTC is either not implemented, or
does not exist at the legacy addresses. OSPM uses the Control
Method Time and Alarm Namespace device instead.
Reserved 10 6 Must be 0.
5.2.9.4 ARM Architecture boot flags
These flags are used by an OS at boot time (before the OS is capable of providing an operating
environment suitable for parsing the ACPI namespace) to determine the code paths to take during
boot. For the PSCI flags, specifically, the flags describe if the platform is compliant with the PSCI
specification. The PSCI specification is found at Links to ACPI-Related Document" (http://uefi.org/
acpi) under the heading PSCI Specification.
The ARM Architecture boot flags are described in Table 5-37:
Table 5-37 Fixed ACPI Description Table ARM Boot Architecture Flags
ARM_BOOT_ARCH
Bit
Length
Bit
Offset
Description
PSCI_COMPLIANT 1 0 1 if PSCI is implemented.
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