On Feb 5, 2011, at 07:59, john gilmore wrote: > > This time around, however, I want to put a more general statement on the > record. Any instruction that operates on a unit shorter in length than its > run-time machine's fetch width is all but certain to be slower than itrs > analogue that operates on a unit equal in length to that fetch width. > What is the fetch width of the z? Is it model-dependent? Are all instructions with operands shorter than the fetch width similar, or is the behavior graduated. For example, is LH slower than L, or are the two similar but both slower than LG?
Isn't the operation of most instructions insensitive to the addressing mode in effect, with the notable exception of LA and its ilk? Is it proper to speak of BSM changing the "AMODE", or the "AMODE in the PSW", or is "AMODE" compiler and Binder terminology only? -- gil
