None - the first number "1" in "1200" means the maximum number of CPUs in a node is one. So there will be no dual socket board for Xeon E3-1200 series.
Any dual socket version will be Intel Xeon Processor 5500 or 5600 capable. The Intel Xeon Processor 3400 E3-1200 series is a single socket solution only.
The new E3-1200 series pedestal only supports 4 drives, so we will be using it strictly in small deploys for SBS 2011 (up to 10 seats or so). In our experience to two limiting factors in any server configuration is I/O and RAM.
The new Intel Server System R1304BTL series 1U 1P will make a good foundation for a physical OS install as well.
For any virtualization tasks we are waiting for a higher end pedestal chassis that will support more than four drives and the same on the 1U platform. We are waiting for a replacement for the Intel Server System SR1695GPRX2AC which is an awesome virtualization platform.
Message was edited by: Philip Elder: Meant to say E3-1200 series not 3400 series.