Intel 820E 2.7.2.3. Direct RDRAM* Ground Plane Reference

Intel® 820E Chipset
R
Design Guide 39
Figure 18. Direct RDRAM* Termination Example
2.7.2.3. Direct RDRAM* Ground Plane Reference
All RSL signals must be referenced to GND to provide the optimal current return path. The Direct
RDRAM ground plane reference must be continuous to the VTERM capacitors. The ground reference
island under the RSL signals must be continuous from the last RIMM to the back of the termination
capacitors. Choose a reference island shape that does not compromise power delivery to the components.
The return current will flow through the VTERM capacitors into the ground island and under the RSL
traces. Any split in the ground island will provide a suboptimal return path. In a four-layer board, this
will require the VTERM island to be on an outer layer. The VTERM island should always be placed on the
top layer.