Maybe and maybe another hacks and also not compiled support for 486 cpus. This hack is invoked only on CPUs, which doesn't support cmpxchg instruction. For example, 486 DLC from Cyrix is basically 386 with i486 instruction set but I'm not able to boot linux for 486 machines. https://en.wikipedia.org/wiki/Cyrix_Cx486DLC But gray386 runs perfectly on 486 DLC without hack involved.