Possible to make MySQL use more than one core?
I actually discussed innodb_thread_concurrency with a MySQL Expert at the Percona Live NYC conference back in May 2011.

I learned something surprising: In spite of the documentation, it is best to leave innodb_thread_concurrency at 0 (infinite concurrency). That way, InnoDB decides the best number of innodb_concurrency_tickets to open for a given MySQL instance setup.

Once you set innodb_thread_concurrency to 0, you can set innodb_read_io_threads and innodb_write_io_threads (both since MySQL 5.1.38) to the maximum value of 64. This should engage more cores.