The DBCC CHECKDB entry (http://msdn.microsoft.com/en-us/library/ms176064.aspx) states that SQL Server always performs parallel checks (excerpt below):
Checking Objects in Parallel
By default, DBCC CHECKDB performs parallel checking of objects. The degree of parallelism is automatically determined by the query processor. The maximum degree of parallelism is configured just like parallel queries. To restrict the maximum number of processors available for DBCC checking, use sp_configure. For more information, see Configure the max degree of parallelism Server Configuration Option. Parallel checking can be disabled by using trace flag 2528. For more information, see Trace Flags (Transact-SQL).
This is incorrect. In Standard Edition (and presumably anything that's not Enterprise), CHECKDB is a single-threaded operation. Only Enterprise Edition performs parallel checking.