The area may be differnet, because each instantiation of the mult may lie under different set of constraints. Say for example, one lies in the critical path, then synopsys will optimize it for timing, increasing its area, while the other if we assume, is in a relaxed timing path, will be optimized for area by synopsys. So each instance of the same DW component can have different area.
Synopsys selects DW components, mostly when you use operators, or when you explicitly instantiate in your design.
you can also hand instantiate them in your design. They are usually found in
$SYNOPSYS/dw
Hope it helps,
kr,
Avi
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