Offsetting Clock Pins in Clamshell Memory Topologies
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Solution Overview
Problem
In clamshell fly-by memory topologies, the double load on signal lines due to shared tapping locations leads to increased reflections and attenuation of high-speed clock signals, which is problematic for high-speed data timing.
Innovation Solution
Offsetting clock package pins to distribute the load along the signal line, with pairs of memory packages connecting at separate locations on the distal edges of their respective memory packages, thereby maximizing separation of signal connections while minimizing stub lengths for lower-speed signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If clock package pins are located at the center of memory packages to reduce stub lengths, then stub length is reduced, but signal reflections and attenuation increase due to double load at shared tapping location
Solution Approach 1:
The patent segments the shared tapping location into two separate tapping locations along the signal line. Instead of both memory packages tapping at the same center location, one package taps at a first location while the other taps at a second location downstream, dividing the concentrated load into distributed loads that reduce reflections and improve signal integrity.
Solution Approach 2:
The patent transitions from a single-point (0D) or two-point at same location (2D) tapping arrangement to a distributed arrangement along the signal line (1D spatial distribution). By offsetting the tapping locations along the length of the signal line, the solution adds a spatial dimension to the load distribution, reducing the concentration of impedance discontinuities.
2Reliability
If clock package pins are offset to distribute load along signal line, then signal integrity improves, but stub lengths for other signals may increase
Solution Approach 1:
The patent applies local quality by making different signal types have different pin location characteristics. Clock signals use offset pins to distribute load and reduce reflections, while other signals can use center-located pins to minimize their stub lengths. This localized optimization allows each signal type to be tuned for its specific performance requirements.
Data Source
AI summary
The disclosed embodiments relate to the design of a memory system which includes a set of one or more memory modules, wherein each memory module in the set has a clamshell configuration, wherein pairs of opposing memory packages containing memory chips are located on opposite sides of the memory module. The memory system also includes a multi-drop path containing signal lines which pass through the set of memory modules, and are coupled to memory packages in the set of memory modules. For a given signal line in the multi-drop path, a first memory package and a second memory package that comprise a given pair of opposing memory packages are coupled to the given signal line at a first location and a second location, respectively, wherein the first location and the second location are separated from each other by a distance d1 along the given signal line.