[figglesonrails]

This isn't surprising. If the set the AC bit on x86, then it will disallow unaligned accesses and you'll be operating in an environment more similar to RISC machines. In order to allow such a thing to succeed, GCC can't produce a 32-bit read from char* address since the alignment is only guaranteed to be 1 (i.e. no alignment) and this would trigger SIGBUS. Thus, in order to get a 32-bit read, you must deref a 32-bit variable, not 4x 8-bit ones. This makes even more sense on RISC systems where this "optimization" would be a tragic bug you'd want to work around in your compiler. See my post with the x86 assembly output confirming your general results.