GNU C Library
Code intended for i686 may fail on some models because they lack a Conditional Move (CMOV) instruction. Compilers asked to optimize code for a more advanced CPU (for example the GNU Compiler with its -march=i686 option) generate code that uses CMOV. Linux systems intended to run on i686 are generally not compatible with these Vortex86 models because the GNU C Library, when built for i686, uses a CMOV instruction in its assembly language strcmp function, which its dynamic loader (ld.so) uses. Hence, no program that uses shared libraries can execute.