AMDZone just posted up their first Hammer FAQ version 1.0.
Q: How much memory will Hammer motherboards support?More information at AMDZone
A: 64 bit extensions allow the 4GB memory barrier to be broken. Desktop and low end workstation boards will initially support up to 4GBs of DDR333 with two DIMM sockets. High end multi CPU boards will support up to 16GBs of DDR333 with 8 DIMM sockets. At this time the theoretical memory limit is far greater than is currently physically possible.