Enabling Beyond-Bound Decoding For DRAM By Unraveling Reed-Solomon Codes


A technical paper titled “Unraveling codes: fast, robust, beyond-bound error correction for DRAM” was published by researchers at Rambus.


“Generalized Reed-Solomon (RS) codes are a common choice for efficient, reliable error correction in memory and communications systems. These codes add 2t extra parity symbols to a block of memory, and can efficiently and reliably correct up to t symbol errors in that block. Decoding is possible beyond this bound, but it is imperfectly reliable and often computationally expensive. Beyond-bound decoding is an important problem to solve for error-correcting Dynamic Random Access Memory (DRAM). These memories are often designed so that each access touches two extra memory devices, so that a failure in any one device can be corrected. But system architectures increasingly require DRAM to store metadata in addition to user data. When the metadata replaces parity data, a single-device failure is then beyond-bound. An error-correction system can either protect each access with a single RS code, or divide it into several segments protected with a shorter code, usually in an Interleaved Reed-Solomon (IRS) configuration. The full-block RS approach is more reliable, both at correcting errors and at preventing silent data corruption (SDC). The IRS option is faster, and is especially efficient at beyond-bound correction of single- or double-device failures. Here we describe a new family of “unraveling” Reed-Solomon codes that bridges the gap between these options. Our codes are full-block generalized RS codes, but they can also be decoded using an IRS decoder. As a result, they combine the speed and beyond-bound correction capabilities of interleaved codes with the robustness of full-block codes, including the ability of the latter to reliably correct failures across multiple devices. We show that unraveling codes are an especially good fit for high-reliability DRAM error correction.”

Find the technical paper here. Published January 2024 (preprint).

Hamburg, Mike, Eric Linstadt, Danny Moore, and Thomas Vogelsang. “Unraveling codes: fast, robust, beyond-bound error correction for DRAM.” arXiv preprint arXiv:2401.10688 (2024).

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