Fly-By Layout For Multiple DRAM Modules

If you plan to use two or more DDR DRAM modules on your board, Efinix recommends using a fly-by layout. This method:

Avoids T-junctions on the PCB thereby improving the SNR.
Reduces the trace lengths between the modules.
The RTT provides the current and matches the impedance with the trace.

If you are only using one module, a fly-by design is not applicable.

Figure 1. Fly-By Example Layouts