What version of SQL relational server is required for PowerPivot?

Dave Wickert answers the question what version of SQL relational server is required for PowerPivot. The question has multiple answers which you can read here:

http://powerpivotgeek.com/2010/01/29/what-database-support-is-needed/

To use as host for the PowerPivot SharePoint services I would say you need to use SQL Server 2008 R2 because without it you won’t be able to install SSAS in integrated mode.