B.P. Singh, Renu Singh:Advanced Microprocessors and Microcontrollers. New Age International, 2002, ISBN 81-224-1425-7, 3.16 Instructions of 80486, S.3–29 (englisch, eingeschränkte Vorschauin der Google-Buchsuche): “The 80486 has 6-new instructions more to that of the 80386 and these are BSWAP → Byte Swap. CMPXCHG → Compare and Exchange. XADD → Exchange and ADD. Byte Swap is especially suitable for downloading of mainframe data on an 80486 system. Little-endian data is stored with the most significant bits at lowest addressed byte. The instruction swap reverses the order of the 4-byte of the 32-bit word thus allowing data conversion from Little-endian format to Big-endian format and vice-versa. Other 2-instrucions CMPXCHG and XADD make multiprocessing and multitasking capabilities more efficient. The other 3-instructions are meant for cache and memory management controls and are used by the system software only.”
