Floating point operations are supported via mandatory SSE2-like instructions, and x87/ MMX style registers are generally not used (but still available even in 64-bit mode) instead, a set of 16 vector registers, 128 bits each, is used.
for stack management) to 16 (fully general), and provides numerous other enhancements. x86-64 also expands general-purpose registers to 64-bit, and expands the number of them from 8 (some of which had limited or fixed functionality, e.g. With 64-bit mode and the new paging mode, it supports vastly larger amounts of virtual memory and physical memory than was possible on its 32-bit predecessors, allowing programs to store larger amounts of data in memory.
It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mode. X86-64 (also known as 圆4, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. The five-volume set of the x86-64 Architecture Programmer's Guide, as published and distributed by AMD in 2002
