Joe, Robs is answer is already saying everything.... but let me give you some more details.
the load (or store) will always do it on a fullword....BUT to do it proper would require doing it with a CS. MVC might on some CPUs appear to do it 4 byte wise (or other multiples thereof) - And again the question: why not do it proper in a code-segment that is fully aware of the multi-CPU environment. Or am I totally of the track and there is in fact a LOAD AND STORE instruction Martin