Each DRH667FB upgrade consists of a matched set of two (eight in the case of the 64GB Kit) DDR2-667 FB-DIMMs. One Advanced Memory Buffer (AMB) is used as the interface between the system memory bus and DIMM DRAMs. One 2K-bit EEPROM is used for Serial Presence Detect. For improved thermal performance, a Full DIMM Heat Spreader with thermal interface material (TIM) is attached to the front and back of the DIMM.