There are two new major features in the new revision: the Pacifica virtualization technology to run multiple operating system simultaneously and Presidio, a technology to boost security. Another major change is the support for DDR2 memory.
The Rev F models also add support for a new memory technology, DDR2. Intel moved from conventional DDR (double data rate) to DDR2 earlier and is now moving from DDR2 to another technology called FB-DIMM (fully buffered dual inline memory modules). FB-DIMM uses the same memory modules as DDR2, but uses a new serial interface that transmits data over a small number of higher-speed electrical links rather than a larger number of parallel wires.Source: CNET.