Encoded Chip Select Signaling for Multi-Rank DRAM Bandwidth
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Solution Overview
Problem
The demand for higher-performance computing in applications like AI, big data analytics, and cloud computing exceeds the bandwidth capabilities of current memory systems, necessitating additional memory ranks that increase pin count and costs, while existing methods fail to efficiently utilize bandwidth per pin.
Innovation Solution
Encoding chip select (CS) bits on one CS pin to select multiple memory ranks, reducing the number of CS pins required by configuring CS signals similar to command bits on the CA pin, allowing more data transfer per pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If additional memory ranks are added to increase bandwidth capability, then memory performance is improved, but pin count and costs increase
Solution Approach 1:
The patent combines multiple chip select functions into a single CS pin by encoding rank selection information. Instead of requiring separate CS pins for each rank (CS0, CS1, CS2, etc.), the invention uses one CS pin that can selectively activate different ranks through encoded command sequences, thereby merging multiple control functions into a single physical pin.
Solution Approach 2:
The CS pin is given multi-functional capability to serve multiple rank selection purposes. A single CS pin can now address and activate any of the four memory ranks (rank 0, rank 1, rank 2, rank 3) by receiving different encoded command patterns, making it a universal control signal that replaces what would traditionally require multiple dedicated pins.
2Productivity
If additional memory ranks are added to increase bandwidth capability, then memory performance is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple control signal functions into existing signal lines. The CS pin and CA pins work together in an encoded scheme where rank selection information is combined with command information, reducing the need for separate dedicated control lines for each rank and thereby simplifying the overall signal line architecture.
3Ease of operation
If traditional chip select methods are used for multiple ranks, then each rank can be selected independently, but bandwidth per pin efficiency decreases
Solution Approach 1:
The patent merges rank selection control with command transmission by encoding the rank information within the command structure itself. The CS pin works in conjunction with encoded CA signals to simultaneously convey both the command type and the target rank information, thereby combining multiple control functions into fewer physical pins and improving bandwidth utilization per pin.
Data Source
AI summary
Systems, apparatus, articles of manufacture, and methods are disclosed for dynamic chip select modes. An example system includes a memory module including a first rank of dynamic random access devices (DRAMs), a second rank of DRAMs, and a third rank of DRAMs, a first signal line coupled to the memory module, a second signal line coupled to the memory module, and a host memory controller coupled to the first and second signal lines, the host memory controller to generate a multi-bit signal that selects the third rank of DRAM devices, and transmit bits of the multi-bit signal over the second signal line over multiple clock cycles.