PCB Expansion Options:
- Optimum
- Rank Slot and Stack Height Expansion
The Versal DDR4 controller supports single slot, dual slot, single rank, and dual rank RDIMM/LRDIMM topologies as well as single slot quad rank LRDIMM devices. For these buffered DIMMs there are two pin maps; Optimum or Rank Slot and Stack Height Expansion. Regardless of the pinout option, the existing pinout will be compatible with x4 and x8 devices without any user intervention.
When the DDRMC is configured for a single rank, single slot, non-3DS based RDIMM device, the default pinout is an efficiently packed Optimum which will only work for these types of devices. The single rank single slot RDIMM is the most efficient buffered DIMM pinout but does not support any additional rank, slot, or 3DS stack height expansion, nor does it support LRDIMM devices. If future hardware revisions may require additional ranks, slots, switch to 3DS devices, or switch to an LRDIMM device then the Rank Slot and Stack Height Expansion option must be selected.
The Rank Slot and Stack Height Expansion option supports all multi-rank, multi-slot, 3DS or standard component based RDIMM/LRDIMM topologies. When an LRDIMM device is selected the only pinout option is Optimum which is the Rank Slot and Stack Height Expansion pinout. When any dual rank or dual slot RDIMM device is selected the only pinout option is Optimum which is the Rank Slot and Stack Height Expansion pinout. When any 3DS based RDIMM or LRDIMM topology is selected then the only pinout option is Optimum which is the Rank Slot and Stack Height Expansion pinout. If your existing hardware design used an LRDIMM device or any multi-rank, or multi-slot, or 3DS based RDIMM device then the hardware already has all the necessary sites allocated for future PCB expansion.