ACPI Component Architecture Programmer Reference

The integer size used by the AML interpreter is variable and is dynamically set via the DSDT that is loaded. For ACPI 1.0 DSDTs with a version number of 1, the integer width used is always 32-bits for backward compatibility. For ACPI 2.0 and later DSDTs with a version number larger than 1, full 64-bit integer math is used. ................
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