AR# 40788: Design Assistant for XST - Help determining discrepancies between the Device Utilization Rerport from XST and PAR.
Design Assistant for XST - Help determining discrepancies between the Device Utilization Rerport from XST and PAR.
Refer to this Answer Record for help understanding why the Device Utilization Summary from XST differs from the Device Utilization Summary from Place and Route.
Note: This Answer Record is a part of the Xilinx Solution Center for XST (Xilinx Answer 38927). The Xilinx Solution Center for XST is available to address all questions related to XST. Whether you are starting a new design or troubleshooting a problem, use the Solution Center for XST to guide you to the right information.
The Device Utilization Report is located at the bottom of XST report, whereas the Device Utilization Report in the PAR report is located at the top. It may surprise one to see that these reports may not correspond with the amount of resources used. Although a little bit of discrepancy may be tolerated, a large amount may raise flags.
A common reason why the XST and PAR Device Utilization Reports may differ is due to optimizations performed during MAP. MAP may trim and/or replicate logic depending on the options chosen when MAP was executed.
Another common reason the XST and PAR Device Utilization Reports may differ is because some of the black boxed components were not read by XST. XST has the option to read Black Boxed netlists and when they are read, the resources within the black boxed netlists are included in the XST report. This XST option is called "Read Cores." This option also must know where your black boxed netlist are placed so that it knows where to read from. The "Cores Search Directories" option points to these directories. The XST report will indicate if the core is being read in the Advanced HDL Synthesis report.