The DDR4 routing rules provided in this chapter allow for the interface to run at the maximum supported data rates as specified in the Versal adaptive SoC data sheets while also assuming a maximum board thickness of 131 mils. For boards thicker than 131 mils, the maximum interface speed might need to be adjusted downward. See the following table for maximum memory data rates per board thickness.
| Component | Board Thickness (mil) | |||
|---|---|---|---|---|
| DDR4 | ≤100 | 101–145 | 101–145 + Stub-free 1 | 145–275 |
| Component | See Versal adaptive SoC data sheets | Two memory speed grades lower from data rates in Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | Three memory speed grades lower from data rates in Versal adaptive SoC data sheets |
| 1-Rank DIMM | See Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | One memory speed grades lower from data rates in Versal adaptive SoC data sheets |
| 2-Rank DIMM | See Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | One memory speed grades lower from data rates in Versal adaptive SoC data sheets |
| 4-Rank DIMM | See Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | See Versal adaptive SoC data sheets | One memory speed grades lower from data rates in Versal adaptive SoC data sheets |
Figure 1. Conventional Routing
Figure 2. Stub-Free Routing
