SXRJC@ALASKA.BITNET (ROBERT J CONCANNON) (12/23/89)
on system 370 machines siof causes the cpu to be released for other work imediately after the channel address work is fetched. sio retains the cpu until after device selection is completed. for siof the actual i/o was asynchronous, but if it ultimately fails the overhead can be more than for sio alone. mvs/xa? i dont know.