I know it's an old thread, but since it's been revived today, Paul White discusses the internals of the various sorts used by SQL Server in these two fairly recent articles:

http://sqlperformance.com/2015/04/sql-plan/internals-of-the-seven-sql-server-sorts-part-1

and

http://sqlperformance.com/2015/05/sql-plan/internals-of-the-seven-sql-server-sorts-part-2

Cheers!