Have you ever experienced significant performance swings in your application after seemingly insignificant changes? A random NOP shifting code addresses causing a 20% speedup or regression? This talk will explore some of the common and not so common architectural reasons why code placement/alignment can affect performance on older and newer x86 processors. Even though ideas will be shared on how to avoid/fix some of these issues in compilers, other very low level issues will not have good compiler solutions, but are still important to recognize for knowledge and identification purposes.