Registered memory

By redistributing the command and address signals within the R-DIMM, this allows more chips to be connected to the memory bus.

[8] Load Reduced DIMM (LR-DIMM or LRDIMM) modules are similar to R-DIMMs, but add a buffer to the data lines as well.

In other words, LR-DIMMs buffer both control and data lines while keeping the parallel nature of all signals.

As a result, LR-DIMMs provide large overall maximum memory capacities, while avoiding the performance and power consumption problems of FB-DIMMs, induced by the required conversion between serial and parallel signal forms.

[7][9] Fully Buffered DIMM (FB-DIMM) modules increase maximum memory capacities in large systems even more, using a more complex buffer chip to translate between the wide bus of standard SDRAM chips and a narrow, high-speed serial memory bus.

Unfortunately, the translation further increased memory latency, and the complex high-speed buffer chips used significant power and generated a lot of heat.