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AR# 12758

sw4.1i PAR - Router incorrectly exits if timing score is zero, but there are still unrouted nets

Description

Keywords: router, routing, unrouted, improving, hang

Urgency: Hot

General Description:
A problem was introduced in 4.1i wherein the router incorrectly exits after the first iteration when the timing score has reached zero, even if there are still unrouted nets.

This bug is in the base router, so it affects all device families. Design with no timing constraints are especially susceptible to this bug, because the auto-timespecing feature generates timing constraints that are easily met.

NOTE: In one case involving a Spartan device, the router appeared to hang after printing "Improving routing". This hang appears to be due to the unusual condition of running cleanup passes on a design with unrouted nets.

Solution

This problem is fixed in the latest 4.1i Service Pack, available at:
http://support.xilinx.com/support/techsup/sw_updates
The first service pack containing the fix is 4.1i Service Pack 2.
AR# 12758
Date Created 08/29/2007
Last Updated 10/20/2008
Status Archive
Type General Article