You find the default system requirements in the overview document: “http://www-01.ibm.com/support/docview.wss?uid=swg27007909[Index of system requirements for Notes, Domino, Domino Administrator, Domino Designer & Notes Traveler]“
I’ve some interesting points. IBM Domino for Windows is available as 32 and 64 bit software, but it is only supported on Windows Server 2008 R2 and Windows Server 2012, so no 32 Bit Windows is supported!
So a lot of us will have to upgrade the OS first.
System Requirements Domino Administrator & Domino Designer 9.0
We got a Linux 64 Bit server the first time in a gold release. I tested it in the beta and it works without any problems.