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"Windows support of UEFI
The following Windows editions include support for UEFI:
• Windows 8.1 and Windows® 8 support native UEFI 2.0 or later on 32-bit (x86), 64-bit (x64), and ARM-based PCs. They also support BIOS-based PCs, and UEFI-based PCs running in legacy BIOS-compatibility mode.
While in UEFI mode, the Windows version must match the PC architecture. A 64-bit UEFI PC can only boot 64-bit versions of Windows. A 32-bit PC can only boot 32-bit versions of Windows. In some cases, while in legacy BIOS mode, you may be able to run 32-bit Windows on a 64-bit PC, assuming the manufacturer supports 32-bit legacy BIOS mode on the PC.
• Windows supports a subset of the functionality that is defined in the UEFI specification. Windows implementations do not explicitly check against higher revisions of the firmware
• For additional UEFI requirements, see UEFI Installation Media Format and default boot behavior and UEFI Requirements: Boot time, Runtime, Hibernation State (S4).