I am using Xilinx XST to synthesize my module. When i set my optimization goal to speed i am able to obtain reduced number of slices and higher Fmax and when i used area for optimization the number of slices got increased and there was a reduction in Fmax. Reduction in Fmax is agreeable as the optimization is with respect to area, but why did the number of slices got increased. Can anyone give me the reason behind it or is there a mistake in my side.
The increase in number of slice does not mean that it utilized more resource. It might have used a little resource of a slice. Just see the LUT utilizations and number of resource used for routing.