Number of Files for tempdb and User Databases

http://travisspencer.com/blog/2008/07/number-of-files-for-tempdb-and.html
http://www.sqllion.com/2009/05/optimizing-tempdb-in-sql-server-2005/
http://searchsqlserver.techtarget.com/tip/0,289483,sid87_gci1276989,00.html
C = Number of CPUs
O = Number of cores per CPU
P = Physical files
To compute the number of files that makeup tempdb, use this formula:
P = C * O
To compute the number of files that makeup user database, use this formula:
P = C * O / 4