AR# 10049: 3.1i Virtex-E PAR - The router doesn't always use a long line when one is available
3.1i Virtex-E PAR - The router doesn't always use a long line when one is available
Keywords: route, router, long, line, timing
Problem Description: A case has been seen where a timing critical signal is routed using a string of many hexes when there are two unused horizontal long lines available in that row. The result is a net with fanout=1 taking 9.944 ns and missing the timing constraint by 4.212 ns.
The problem was found to be due to a problem in router cost calculation specific to the -7 speed grade.