FB-DIMM is short for Fully-Buffered Dual Inline Memory Module and is a kind of DDR2 memory developed for high-pressure systems such as servers where large amounts of memory with high reliability is required. FB-DIMM is a serial data transfering technology such as Serial ATA and PCI Express. FB-DIMM modules use a serial bus with an AMB chip (Advanced Memory Buffer) that connect the memory modules into one channel. With up to 6 channels with 8 FB-DIMM modules per channel the technology sports up to 192GB memory on a single memory controller, a great advantage to regular DDR2 technology that support 4 memory modules with two channels. At HotHardware they’ve come across some FB-DIMM modules from Kingston and took some pictures.
With the heatspreader removed you can clearly see the AMB chip in the middle. It keeps track of all the data packages and the contact with the other modules in the system and the memory controller.