AR# 5686: 1.5i XC4000XL PAR - Router fails to meet timing on TBUF nets, but re-route is successful.
1.5i XC4000XL PAR - Router fails to meet timing on TBUF nets, but re-route is successful.
Cases have been seen where PAR failed to meet timing on paths containing multiple driver TBUF nets, but it was noticed that re-entrant routes using PAR or EPIC easily met timing. This problem is due to to a bug where PAR routes and locks nets during the "pre-assignment phase", but fails to later unlock the nets as it should.
A re-entrent route or re-route in EPIC is successful because the net locking mechanism is gone.
This problem is fixed in vesion 2.1i, currently scheduled for 6/99. Meanwhile the problem can be re-routed by using a re-entrant routing pass.