A problem has been seen running par on high density devices (4085xl and 40125xv) where if all of the I/O's available are being used, PAR is unable to successfully place all the I/O. PAR fails with the Warning:
WARNING:baspl:291 - The IOB component "io<0>" could not be placed. ERROR:baspl:292 - This is probably due either to lack of resources or to preference conflicts. If PAR has been run, please check the .par file for resource allocation and utilization and verify that there are sufficient resources to place the component(s). Also ensure that all placement conflicts have been resolved.
A work around is to lock down the pins in pcf or ucf file.
This issue is being investigated. Meanwhile a work around is to lock down the pins that are having the problem.
The syntax for ucf file is as follows: NET mynet LOC = P12;