To give an example, iirc on sparc, unaligned access traps. And iirc, on older arm (before armv7), it would read at the clamped aligned address, and rotate the bits to match the unaligned address (eg if your aligned data is abcdef and you read 4 bytes at offset 2, you actually read cdab). I think you can still get this behavior on armv7 if you want.