Memory module with timing-controlled data buffering

What is this patent about?

’506 is related to the field of high-speed memory modules, specifically multi-rank dual in-line memory modules (DIMMs) that utilize a distributed buffering architecture. It addresses the technical challenges of maintaining signal integrity and precise timing synchronization as memory bus speeds increase and data windows shrink. The background context involves the difficulty of managing signal propagation delays and electrical loading across large numbers of memory chips, where traditional centralized control often fails to compensate for the physical distance between components on the module board.

The underlying idea behind ’506 is to decentralize the timing control by placing distributed buffer circuits directly between the memory controller and specific groups of memory devices. Instead of relying on the system memory controller to manage the complex flight-time variations of every individual chip, the invention shifts the responsibility to these local buffers. The key inventive insight is the use of a dynamic delay mechanism within each buffer that calculates the necessary timing offset based on signals observed during previous operations, effectively allowing the module to self-calibrate and align data edges locally.

The claims of ’506 focus on a memory module architecture where a central module control device manages command/address signals while a plurality of data buffers manage the data path. Specifically, the independent claims cover a mechanism where a data buffer receives module control signals and, in response, applies a predetermined delay to a read strobe signal received from a memory device. This delayed strobe is then used to sample the read data before it is transmitted to the system data bus, ensuring that the data is handed off to the memory controller with precise timing that accounts for board-level latencies.

In practice, the invention functions by having each buffer monitor the time interval between receiving a control signal from the module controller and receiving a strobe signal from the system controller during a write operation. This measured interval, which captures the unique physical propagation delay for that specific buffer's location on the board, is stored and used to program a delay circuit. When a subsequent read operation occurs, the buffer applies this learned timing to the outgoing data, ensuring the read data arrives at the memory controller exactly when expected according to the system's latency parameters.

This approach differs from prior solutions by moving away from fixed-length 'fly-by' wiring topologies or total reliance on the memory controller’s leveling capabilities. By implementing local synchronization at the buffer level, the invention mitigates the effects of process, voltage, and temperature variations that typically cause timing drift. Furthermore, it allows the module to support more memory ranks than the controller is natively designed to handle, as the buffers act as an abstraction layer that presents a simplified electrical load and a unified timing interface to the host system.