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AR# 62720

Vivado Implementation - Placer reports higher LUTs utilization in "ERROR: [Place 30-380]" than what is seen in the post-opt utilization report


Placer fails with the following error:

ERROR: [Place 30-380] Design has 46680 flops (which belong to 2202 control sets and 0 of them are latches) and 48516 luts. Their placement requires at least 11598 slices but the device has only 11550 slices.

However, in the post-opt utilization report, the LUTs utilization is 39289, which is less than 48516 mentioned in the error message.

Where does the extra LUTs utilization come from?


The extra LUTs utilization comes from the LUTs used as pack through - also known as route through.

These LUTs are counted into utilization starting from placement.

After placement, you can show the total LUTs utilization including pack through by running the Tcl command below in the Tcl console in implemented design:
report_utilization -packthru
AR# 62720
Date 01/19/2015
Status Active
Type General Article
  • Vivado Design Suite
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