208 Optimizing with SIMD Instructions Chapter 9
25112 Rev. 3.06 September 2005
Software Optimization Guide for AMD64 Processors
9.8 Passing Data between MMX™ and 3DNow!™
Instructions
Optimization
Avoid passing data between MMX and 3DNow!™ instructions.
Application
This optimization applies to:
• 32-bit software
• 64-bit software
Rational
The AMD Athlon 64 and AMD Opteron processors do not support bypassing register data between
MMX and 3DNow! instructions. One additional cycle of latency is added to a dependency chain
whenever data is passed between these instruction groups in either direction.