shekita@crystal.UUCP (06/24/85)
Are there any alignment constraints on the Vax 780? Could one, for example, set an integer pointer to the middle of a machine word? If there aren't alignment constraints, is it faster to compare two word-aligned integers?
stew@harvard.ARPA (Stew Rubenstein) (06/26/85)
> Are there any alignment constraints on the Vax 780? > Could one, for example, set an integer pointer to > the middle of a machine word? > > If there aren't alignment constraints, is it faster > to compare two word-aligned integers? There are no constraints, but there is definitely a speed penalty for fetching non-aligned data. longwords should be aligned on longword boundaries, quadwords on quadwords, etc., for best performance. I have even heard of differences in benchmark timing based on the alignment of the instruction stream, though this is harder to predict and control.