title: Does running a SQL Server 2005 database in compatibility level 80 have a negative impact on performance?
body: <p>Our software must be able to run on SQL Server 2000 and 2005.  To simplify development, we're running our SQL Server 2005 databases in compatibility level 80.  However, database performance seems slower on SQL 2005 than on SQL 2000 in some cases (we have not confirmed this using benchmarks yet).  Would upgrading the compatibility level to 90 improve performance on the SQL 2005 servers?</p>