x64

Architecture of CPU #

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x86 x86-64 (also known as x64, x86_64, AMD64, and Intel 64)

is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mode.

wikipedia

Backward compatibility in x64 #

The compatibility mode defined in the architecture allows 16- and 32-bit user applications to run unmodified, coexisting with 64-bit applications if the 64-bit operating system supports them.[11][note 2] As the full x86 16-bit and 32-bit instruction sets remain implemented in hardware without any intervening emulation, these older executables can run with little or no performance penalty,[13] while newer or modified applications can take advantage of new features of the processor design to achieve performance improvements.