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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 V
TERM
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 V
TERM
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 V
TERM
island to be on an outer layer. The V
TERM
island should always be placed on the
top layer.