Fully Buffered DIMM

A Fully Buffered DIMM (FB-DIMM) is a type of memory module used in computer systems.

As the memory width increases together with the access speed, the signal degrades at the interface between the bus and the device.

This limits the speed and memory density, so FB-DIMMs take a different approach to solve the problem.

Unlike the parallel bus architecture of traditional DRAMs, an FB-DIMM has a serial interface between the memory controller and the AMB.

The AMB can also offer error correction, without imposing any additional overhead on the processor or the system's memory controller.

It can also use the Bit Lane Failover Correction feature to identify bad data paths and remove them from operation, which dramatically reduces command/address errors.

[8] FB-DIMMS have 240 pins and are the same total length as other DDR DIMMs but differ by having indents on both ends within the slot.

[citation needed] The cost of FB-DIMM memory was initially much higher than registered DIMM, which may be one of the factors behind its current level of acceptance.

Although strenuous efforts were made to minimize delay in the AMB, there is some noticeable cost in memory access latency.

[13] In addition, AMD also developed Socket G3 Memory Extender (G3MX), which uses a single buffer for every 4 modules instead of one for each, to be used by Opteron-based systems in 2009.

[14] At the 2007 Intel Developer Forum, it was revealed that major memory manufacturers have no plans to extend FB-DIMM to support DDR3 SDRAM.