Segmentation was expensive (loading an 80286 segment register was very slow and the segment table was impractically small) but could express "offsets between 0

Segmentation was expensive (loading an 80286 segment register was very slow and the segment table was impractically small) but could express "offsets between 0 and 42 are valid". Paging is much coarser and suffers from false negatives, because x[y] might accidentally walk off the end of x, skip a guard page, and land on a mapped page from another object.