Another bonus quirk, from the 486 and Pentium area..
BSWAP EAX converts from little endian to big endian and vice versa. It was a 32 bit instruction to begin with.
However, we have the 0x66 prefix that switches between 16 and 32 bit mode. If you apply that to BSWAP EAX undefined funky things happen.
On some CPU architectures (Intel vs. AMD) the prefix was just ignored. On others it did something that I call an "inner swap". E.g. in your four bytes that are stored in EAX byte 1 and 2 are swapped.
Unfortunately I have not found any evidence nor reason to believe that this "inner swap" behaviour you mention exists in some CPU --- except perhaps some flawed emulators?
BSWAP EAX converts from little endian to big endian and vice versa. It was a 32 bit instruction to begin with.
However, we have the 0x66 prefix that switches between 16 and 32 bit mode. If you apply that to BSWAP EAX undefined funky things happen.
On some CPU architectures (Intel vs. AMD) the prefix was just ignored. On others it did something that I call an "inner swap". E.g. in your four bytes that are stored in EAX byte 1 and 2 are swapped.