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X86-64: Difference between revisions
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Added information about notifying the BIOS of the intended target environment
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m (This looks really bad and I know a much cleaner way of doing it that I really need to document) |
(Added information about notifying the BIOS of the intended target environment) |
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There is also [[Entering Long Mode Directly|an example]] of this implemented in a [[bootloader]].
== Notifying the BIOS ==
In order for the firmware built into the system to optimize itself for running in Long Mode, AMD recommends that the OS notify the BIOS about the intended target environment that the OS will be running in: 32-bit mode, 64-bit mode, or a mixture of both modes. This can be done by calling the BIOS interrupt 15h from Real Mode with AX set to 0xEC00, and BL set to 1 for 32-bit Protected Mode, 2 for 64-bit Long Mode, or 3 if both modes will be used.
== 64 bit Environment Models ==
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