AMD64 technology

Table 1. 32-bit x86 instructions common to AMD processors

Instruction	Description	Register	Size of	Number of
name		type	registers	registers

Standard	Instructions for logical and arithmetic operations, address	GPR	32-bit	8
x86	calculations, and has 16-bit index registers for memory
	pointers

MMX	Multimedia instructions that allow the processor to do 64-bit	MMX	64-bit	8
	SIMD operations

x87	Instructions for floating point calculations	FP	80-bit*	8

SSE, SSE2,	SSE improved upon the MMX instructions and allowed	MMX	128-bit	8
SSE3, and	processors to do 128-bit SIMD floating-point operations.
SSE4a	SSE2 added 64-bit parallel floating point numeric support.
	SSE2 added 64-bit parallel floating point numeric support.

It also added new instructions to support 128-bit SIMD integer operations.

SSE3 instructions include 13 instructions that accelerate performance of SSE technology, SSE2 technology, and x87-floating-point math capabilities.

SSE4a instructions include two new SSE instructions. SSE4a instructions also add support for unaligned SSE load- operation, which formerly required 16-byte alignment.

*According to the article “An Introduction to 64-bit Computing and x86-64” by Jon Stokes1, the “x87 uses 80-bit registers to do double-precision floating point. The floats themselves are 64-bit, but the processor converts them to an internal, 80-bit format for increased precision when doing computations.”

AMD Opteron processors support the AMD 3Dnow!™ instruction set, AMD’s version of multimedia instructions. The 3DNow! set added SIMD instructions to improve the vector-processing (floating point) performance of graphic-intensive and multimedia applications.

Introduced in 2003, AMD64 technology is the AMD microarchitecture and instruction set that provides full support for 64-bit operating systems and applications. The most important feature of AMD64 is support for very large virtual and physical memory in a flat address space.

Instruction set and registers

AMD64 instructions can take advantage of the 64-bit wide registers in AMD Opteron processors. These registers are used by the applications only when running the processors in 64-bit long mode. To support the AMD64 instructions, the registers expand to include the following:

•Eight new 64-bit GPRs

•Extensions of the eight original, 32-bit GPRs to 64 bits

•Eight new 128-bit registers for SSE, SSE2, and SSE3 instructions

1Available at http://arstechnica.com/cpu/03q1/x86-64/x86-64-1.html