Intel 820E manual Direct RDRAM* Ground Plane Reference, Direct RDRAM* Termination Example

Intel® 820E Chipset

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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.

Design Guide 39