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AR# 11103

3.1i Virtex PAR - "Error: DesignRules:475 - Netcheck: Improper routing. Signal INT_DPRA<0> is routed with far too many unbuffered connections...."


Keywords: BitGen, PAR, Design Rules, 475, Netcheck, improper routing, unbuffered, CORE Generator, COREGen, Distributed Memory.

Urgency: Standard

General Description:
I have a large CORE Generator module (such as Distributed Memory v4) in my design, and I encounter the following error when running BitGen:

ERROR:DesignRules:475 - Netcheck: Improper routing. Signal INT_DPRA<0> is routed with far too many unbuffered connections. This net must be rerouted. To resolve this error, please consult the answers database at http://support.xilinx.com


This is actually a routing issue, not a BitGen issue. The problem is detected by BitGen because DRC is first run by default during BitGen. The problem is flagged when the router strings together too many unbuffered resources to make a connection. 3.1i Service Pack 8 fixes a specific known problem whereby the router sometimes introduces this problem in certain CORE Generator modules.

NOTE: This issue affects the Virtex, Virtex-E and Spartan-II device architectures.

This problem is fixed in the latest 3.1i Service Pack, available at:
The first service pack containing the fix is 3.1i Service Pack 8.
AR# 11103
Date Created 08/29/2007
Last Updated 10/22/2008
Status Archive
Type General Article