Memory module with data buffering

What is this patent about?

’417 is related to the field of high-density memory modules, specifically focusing on architectures that allow a memory module to support more physical memory ranks than a standard memory controller is designed to address. It addresses the technical challenges of signal integrity, electrical loading, and timing synchronization that arise when increasing the number of memory devices on a single printed circuit board.

The underlying idea behind ’417 is to decouple the physical memory devices from the system memory bus by using an intelligent intermediary layer that manages both control signals and data paths. By implementing a logic-controlled buffer, the invention allows the module to present a simplified electrical load to the controller while internally managing a more complex array of memory ranks. This insight allows for load isolation, where the high capacitive load of multiple memory chips is hidden from the memory controller, enabling higher speeds and greater capacities.

The claims of ’417 focus on a memory module architecture that utilizes logic to receive input chip-select signals and output registered address and control signals to specific N-bit wide ranks. A critical aspect of the independent claims is the inclusion of specialized circuitry positioned between the memory bus and the data pins of the memory devices. This circuitry is controlled by data buffer signals and is specifically configured to operate with an overall CAS latency that is intentionally higher than the actual operational latency of the individual memory chips.

In practice, the invention works by registering data transfers through the intermediary circuitry for a specific time delay, typically at least one clock cycle. This extra cycle provides the necessary timing budget for the logic to decode commands and route data to the correct physical rank without violating the strict timing requirements of the high-speed memory bus. The data buffer control signals dynamically enable and disable data paths, ensuring that only the active rank is electrically visible to the bus during a read or write operation.

This approach differs from prior solutions by moving beyond simple signal buffering to a comprehensive rank multiplication strategy that is transparent to the host system. While traditional modules are limited by the number of chip-select lines provided by the controller, ’417 uses its internal logic and registered data paths to simulate a virtual memory configuration. This allows the use of lower-density, cost-effective memory chips to achieve the performance and capacity of much more expensive, higher-density components while maintaining superior signal integrity.