During XST synthesis, the following warning occurs:
"WARNING:Xst:643 - Multiplier result width is N bits."
This warning occurs when the maximum width of an inferred multiplier is not created.
Given the following:
C = A * B;
width (C) = width (A) + width (B)
when the width of C is less than the sum of the widths of A and B, that width will be represented by "N" in the warning.