The following figure shows the Nibble utilization for the 72-bit, Multi-Rank
L/RDIMM interface with ECC in the flipped configuration. DQ indicates a data nibble,
AC indicates an Address/Command/Control nibble, 
sys_clk indicates a nibble comprising the System Clock pair, RESET_n,
and ALERT_n.Important: The nibble utilization figure is based on the fixed pinout
output by Vivado for this
configuration.
Figure 1. Nibble Utilization for 72-bit Multi-Rank L/RDIMM with
ECC (Flipped)