MS SQL Server Express CPU The specs say "limited to the lesser of 1 socket or 4 cores" however if you have two express instances on the same server and that server has 8 cores CPU 0-7, is it possible to assign instance 1 to CPU 0-3 and instance 2 to CPU 4-7?
SQL Server Express Edition will honor the specified processor affinity settings but not more than the 4 core edition limitation.  I don't think it's defined which 4 cores are used if you specify more than 4.  Note that unlike other SQL Server editions, a service restart is required for changes to take affect.