Rainer Plitschka
Agilent Technologies

Higher CPU speeds drive the need for higher memory bandwidth. For decades, CPUs have connected to the memory using a parallel synchronous bus, running at speeds up to a couple of hundred MHz. However, the speed of DDR2 technology, for example, limits the number of DIMMs in a system because of the multi-drop routing necessary. At the same time, other PC interfaces have successfully migrated to gigabit speed, multiple-serial connections. These overcome the technological problems at reasonable costs.

A new multiple serial interface, called Fully Buffered DIMM (FBD), applies this concept to memory interfaces. It uses Advanced Memory Buffer AMB) chips to connect the CPU to the memory at gigabit speeds.