Filter
Top Products
4 Introduction Chapter 1
25112 Rev. 3.06 September 2005
Software Optimization Guide for AMD64 Processors
1.4 Important New Terms
This section defines several important terms and concepts used in this guide.
Primitive Operations
AMD Athlon 64 and AMD Opteron processors perform four types of primitive operations:
• Integer (arithmetic or logic)
• Floating-point (arithmetic)
• Load
• Store
Internal Instruction Formats
The AMD64 instruction set is complex; instructions have variable-length encodings and many
perform multiple primitive operations. AMD Athlon 64 and AMD Opteron processors do not execute
these complex instructions directly, but, instead, decode them internally into simpler fixed-length
instructions called macro-ops. Processor schedulers subsequently break down macro-ops into
sequences of even simpler instructions called micro-ops, each of which specifies a single primitive
operation.
A macro-op is a fixed-length instruction that:
• Expresses, at most, one integer or floating-point operation and one load and/or store operation.
• Is the primary unit of work managed (that is, dispatched and retired) by the processor.
A micro-op is a fixed-length instruction that:
• Expresses one and only one of the primitive operations that the processor can perform (for
example, a load).
• Is executed by the processor’s execution units.