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x86-64 is a computer term for a 64-bit microprocessor architecture that is an extension of the older, 32-bit x86 architecture. Also known as x64, x86_64, AMD64, and Intel 64, this architecture is the standard for most modern personal computers and servers today.

Key features

Larger memory addressing: The most significant advantage of x86-64 is its support for a vastly larger amount of addressable memory (RAM). While a 32-bit system is limited to roughly 4 gigabytes (GB) of RAM, x86-64 systems can theoretically access up to 16 exabytes (EB).

Backward compatibility: x86-64 is designed to be fully backward-compatible with its 32-bit predecessors. This means that a 64-bit processor can run both 64-bit and 32-bit software without a significant performance penalty. This differs from Intel's earlier, incompatible Itanium architecture (IA-64), which was a commercial failure.

Improved performance: With the ability to process 64 bits of data at once, the architecture provides a boost to applications that perform intensive calculations or work with large datasets. It also doubles the number of general-purpose registers available to software, which can lead to faster execution for certain tasks.

Advanced instruction sets: The x86-64 architecture includes optional advanced instructions for optimizing specific tasks. Examples include Advanced Vector Extensions (AVX) for vector operations and instructions for cryptographic operations.

Security enhancements: Most x86-64 CPUs include a "no-execute" (NX) bit in the memory page table. This allows the system to mark memory regions as read-only, which helps prevent buffer overflow attacks by blocking code execution from data areas.