The main change for the 430X architecture was the introduction of a 20-bit address range that allows addressing outside 64 KB on the original 430 devices. There is a new set of instructions that work with a 20-bit address in parallel with 16-bit old-style instructions. eg
CALL ; takes a 16 bit address
CALLA ; takes a 20 bit address
PUSH ; Push the bottom 16 bits of a register onto the stack
PUSHA ; Push the full 20 bit register
, 430, 64- 430X. (IAR , , Rowley) , 430X , , 64K.